util: error: Fix error message strings to play well with additional info

Additional information for an error message is either in form of a
string or empty. Fix two offenders. One used %d as the format modifier
and the second one  always expected a string.

Thankfully, neither of the offenders are currently in effect.
Signed-off-by: NPeter Krempa <pkrempa@redhat.com>
Reviewed-by: NErik Skultety <eskultet@redhat.com>

src/util/virerror.c

@@ -975,7 +975,10 @@ virErrorMsg(virErrorNumber error, const char *info)
                 errmsg = _("POST operation failed");
             break;
         case VIR_ERR_HTTP_ERROR:
-            errmsg = _("got unknown HTTP error code %d");
+            if (info != NULL)
+                errmsg = _("got unknown HTTP error code %s");
+            else
+                errmsg = _("got unknown HTTP error code");
             break;
         case VIR_ERR_UNKNOWN_HOST:
             if (info != NULL)
@@ -1002,7 +1005,10 @@ virErrorMsg(virErrorNumber error, const char *info)
                 errmsg = _("could not connect to Xen Store %s");
             break;
         case VIR_ERR_XEN_CALL:
-            errmsg = _("failed Xen syscall %s");
+            if (info == NULL)
+                errmsg = _("failed Xen syscall");
+            else
+                errmsg = _("failed Xen syscall %s");
             break;
         case VIR_ERR_OS_TYPE:
             if (info == NULL)