Check return status for virUUIDGenerate

Although legal, a few paths were not checking a return value < 0
for failure instead they checked a non zero failure.

Clean them all up to be consistent.
Signed-off-by: NJohn Ferlan <jferlan@redhat.com>

src/conf/domain_conf.c

@@ -18801,7 +18801,7 @@ virDomainDefParseXML(xmlDocPtr xml,
      * also serve as the uuid. */
     tmp = virXPathString("string(./uuid[1])", ctxt);
     if (!tmp) {
-        if (virUUIDGenerate(def->uuid)) {
+        if (virUUIDGenerate(def->uuid) < 0) {
             virReportError(VIR_ERR_INTERNAL_ERROR,
                            "%s", _("Failed to generate UUID"));
             goto error;

src/conf/network_conf.c

@@ -1619,7 +1619,7 @@ virNetworkDefParseXML(xmlXPathContextPtr ctxt)
     /* Extract network uuid */
     tmp = virXPathString("string(./uuid[1])", ctxt);
     if (!tmp) {
-        if (virUUIDGenerate(def->uuid)) {
+        if (virUUIDGenerate(def->uuid) < 0) {
             virReportError(VIR_ERR_INTERNAL_ERROR,
                            "%s", _("Failed to generate UUID"));
             goto error;

src/conf/secret_conf.c

@@ -177,7 +177,7 @@ secretXMLParseNode(xmlDocPtr xml, xmlNodePtr root)
 
     uuidstr = virXPathString("string(./uuid)", ctxt);
     if (!uuidstr) {
-        if (virUUIDGenerate(def->uuid)) {
+        if (virUUIDGenerate(def->uuid) < 0) {
             virReportError(VIR_ERR_INTERNAL_ERROR,
                            "%s", _("Failed to generate UUID"));
             goto cleanup;

src/openvz/openvz_conf.c

@@ -1019,7 +1019,7 @@ openvzSetUUID(int vpsid)
 {
     unsigned char uuid[VIR_UUID_BUFLEN];
 
-    if (virUUIDGenerate(uuid)) {
+    if (virUUIDGenerate(uuid) < 0) {
         virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
                        _("Failed to generate UUID"));
         return -1;

src/xenconfig/xen_common.c

@@ -202,7 +202,7 @@ xenConfigGetUUID(virConfPtr conf, const char *name, unsigned char *uuid)
     }
 
     if (!(val = virConfGetValue(conf, name))) {
-        if (virUUIDGenerate(uuid)) {
+        if (virUUIDGenerate(uuid) < 0) {
             virReportError(VIR_ERR_INTERNAL_ERROR,
                            "%s", _("Failed to generate UUID"));
             return -1;