Fix leak of comment string if virConfAddEntry fails on OOM

The code parsing comments in config files called virConfAddEntry
but did not check for failure. This caused the comment string to
leak on OOM.
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>

src/util/virconf.c

@@ -589,7 +589,10 @@ virConfParseComment(virConfParserCtxtPtr ctxt)
     while ((ctxt->cur < ctxt->end) && (!IS_EOL(CUR))) NEXT;
     if (VIR_STRNDUP(comm, base, ctxt->cur - base) < 0)
         return -1;
-    virConfAddEntry(ctxt->conf, NULL, NULL, comm);
+    if (virConfAddEntry(ctxt->conf, NULL, NULL, comm) == NULL) {
+        VIR_FREE(comm);
+        return -1;
+    }
     return 0;
 }