cgroup: avoid leaking a file

Clang detected a dead store to rc.  It turns out that in fixing this,
I also found a FILE* leak.

This is a subtle change in behavior, although unlikely to hit.  The
pidfile is a kernel file, so we've probably got more serious problems
under foot if we fail to parse one.  However, the previous behavior
was that even if one pid file failed to parse, we tried others,
whereas now we give up on the first failure.  Either way, though,
the function returns -1, so the caller will know that something is
going wrong, and that not all pids were necessarily reaped.  Besides,
there were other instances already in the code where failure in the
inner loop aborted the outer loop.

* src/util/cgroup.c (virCgroupKillInternal): Abort rather than
resuming loop on fscanf failure, and cleanup file on error.

src/util/cgroup.c

@@ -1351,7 +1351,9 @@ static int virCgroupKillInternal(virCgroupPtr group, int signum, virHashTablePtr
     int killedAny = 0;
     char *keypath = NULL;
     bool done = false;
-    VIR_DEBUG("group=%p path=%s signum=%d pids=%p", group, group->path, signum, pids);
+    FILE *fp = NULL;
+    VIR_DEBUG("group=%p path=%s signum=%d pids=%p",
+              group, group->path, signum, pids);
 
     rc = virCgroupPathOfController(group, -1, "tasks", &keypath);
     if (rc != 0) {
@@ -1364,7 +1366,6 @@ static int virCgroupKillInternal(virCgroupPtr group, int signum, virHashTablePtr
      */
     while (!done) {
         done = true;
-        FILE *fp;
         if (!(fp = fopen(keypath, "r"))) {
             rc = -errno;
             VIR_DEBUG("Failed to read %s: %m\n", keypath);
@@ -1376,7 +1377,8 @@ static int virCgroupKillInternal(virCgroupPtr group, int signum, virHashTablePtr
                     if (feof(fp))
                         break;
                     rc = -errno;
-                    break;
+                    VIR_DEBUG("Failed to read %s: %m\n", keypath);
+                    goto cleanup;
                 }
                 if (virHashLookup(pids, (void*)pid))
                     continue;
@@ -1403,6 +1405,7 @@ static int virCgroupKillInternal(virCgroupPtr group, int signum, virHashTablePtr
 
 cleanup:
     VIR_FREE(keypath);
+    VIR_FORCE_FCLOSE(fp);
 
     return rc;
 }