virsh: Refactor parseRateStr to avoid false-positive uninitialized variable

Commit 6983d6d2 tried to improve parseRateStr but broke the build
instead for compilers that were not able to properly introspect the for
loop indexed by the enum resulting into the following error:

virsh-domain.c: In function 'parseRateStr':
virsh-domain.c:916:13: error: 'field_name' may be used uninitialized in this function [-Werror=maybe-uninitialized]
             vshError(ctl, _("malformed %s field"), field_name);
             ^
virsh-domain.c:915:13: error: 'tmp' may be used uninitialized in this function [-Werror=maybe-uninitialized]
         if (virStrToLong_ullp(token, NULL, 10, tmp) < 0) {
             ^
Rather than trying to fix the code, refactor the function again by
reusing virStringSplit.

tools/virsh-domain.c

@@ -863,67 +863,49 @@ static const vshCmdOptDef opts_attach_interface[] = {
 };
 
 /* parse inbound and outbound which are in the format of
- * 'average,peak,burst', in which peak and burst are optional,
+ * 'average,peak,burst,floor', in which peak and burst are optional,
  * thus 'average,,burst' and 'average,peak' are also legal. */
-static int parseRateStr(vshControl *ctl,
+
+#define VSH_PARSE_RATE_FIELD(index, name)                                      \
+    do {                                                                       \
+        if (index < ntok &&                                                    \
+            *tok[index] != '\0' &&                                             \
+            virStrToLong_ullp(tok[index], NULL, 10, &rate->name) < 0) {        \
+            vshError(ctl, _("field '%s' is malformed"), #name);                \
+            goto cleanup;                                                      \
+        }                                                                      \
+    } while (0)
+
+static int
+vshParseRateStr(vshControl *ctl,
                 const char *rateStr,
                 virNetDevBandwidthRatePtr rate)
 {
-    char *token;
-    char *next;
-    char *saveptr = NULL;
-    enum {
-        AVERAGE, PEAK, BURST, FLOOR
-    } state;
+    char **tok = NULL;
+    size_t ntok;
     int ret = -1;
 
-    if (!rateStr)
+    if (!(tok = virStringSplitCount(rateStr, ",", 0, &ntok)))
         return -1;
 
-    next = vshStrdup(ctl, rateStr);
-
-    for (state = AVERAGE; state <= FLOOR; state++) {
-        unsigned long long *tmp;
-        const char *field_name;
-
-        if (!(token = strtok_r(next, ",", &saveptr)))
-            break;
-        next = NULL;
-
-        switch (state) {
-        case AVERAGE:
-            tmp = &rate->average;
-            field_name = "average";
-            break;
-
-        case PEAK:
-            tmp = &rate->peak;
-            field_name = "peak";
-            break;
-
-        case BURST:
-            tmp = &rate->burst;
-            field_name = "burst";
-            break;
-
-        case FLOOR:
-            tmp = &rate->floor;
-            field_name = "floor";
-            break;
-        }
-
-        if (virStrToLong_ullp(token, NULL, 10, tmp) < 0) {
-            vshError(ctl, _("malformed %s field"), field_name);
+    if (ntok > 4) {
+        vshError(ctl, _("Rate string '%s' has too many fields"), rateStr);
         goto cleanup;
     }
-    }
+
+    VSH_PARSE_RATE_FIELD(0, average);
+    VSH_PARSE_RATE_FIELD(1, peak);
+    VSH_PARSE_RATE_FIELD(2, burst);
+    VSH_PARSE_RATE_FIELD(3, floor);
 
     ret = 0;
  cleanup:
-    VIR_FREE(next);
+    virStringFreeList(tok);
     return ret;
 }
 
+#undef VSH_PARSE_RATE_FIELD
+
 static bool
 cmdAttachInterface(vshControl *ctl, const vshCmd *cmd)
 {
@@ -979,7 +961,7 @@ cmdAttachInterface(vshControl *ctl, const vshCmd *cmd)
 
     if (inboundStr) {
         memset(&inbound, 0, sizeof(inbound));
-        if (parseRateStr(ctl, inboundStr, &inbound) < 0)
+        if (vshParseRateStr(ctl, inboundStr, &inbound) < 0)
             goto cleanup;
         if (!inbound.average && !inbound.floor) {
             vshError(ctl, _("either inbound average or floor is mandatory"));
@@ -988,7 +970,7 @@ cmdAttachInterface(vshControl *ctl, const vshCmd *cmd)
     }
     if (outboundStr) {
         memset(&outbound, 0, sizeof(outbound));
-        if (parseRateStr(ctl, outboundStr, &outbound) < 0)
+        if (vshParseRateStr(ctl, outboundStr, &outbound) < 0)
             goto cleanup;
         if (outbound.average == 0) {
             vshError(ctl, _("outbound average is mandatory"));
@@ -3307,7 +3289,7 @@ cmdDomIftune(vshControl *ctl, const vshCmd *cmd)
     memset(&outbound, 0, sizeof(outbound));
 
     if (inboundStr) {
-        if (parseRateStr(ctl, inboundStr, &inbound) < 0)
+        if (vshParseRateStr(ctl, inboundStr, &inbound) < 0)
             goto cleanup;
         /* we parse the rate as unsigned long long, but the API
          * only accepts UINT */
@@ -3349,7 +3331,7 @@ cmdDomIftune(vshControl *ctl, const vshCmd *cmd)
     }
 
     if (outboundStr) {
-        if (parseRateStr(ctl, outboundStr, &outbound) < 0)
+        if (vshParseRateStr(ctl, outboundStr, &outbound) < 0)
             goto cleanup;
         if (outbound.average > UINT_MAX || outbound.peak > UINT_MAX ||
             outbound.burst > UINT_MAX) {