Fix typo in identity code which is pre-requisite for CVE-2013-4311

The fix for CVE-2013-4311 had a pre-requisite enhancement
to the identity code

  commit db7a5688
  Author: Daniel P. Berrange <berrange@redhat.com>
  Date:   Thu Aug 22 16:00:01 2013 +0100

    Also store user & group ID values in virIdentity

This had a typo which caused the group ID to overwrite the
user ID string. This meant any checks using this would have
the wrong ID value. This only affected the ACL code, not the
initial polkit auth. It also leaked memory.
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>
(cherry picked from commit e4697b92)

src/rpc/virnetserverclient.c

@@ -683,7 +683,7 @@ virNetServerClientCreateIdentity(virNetServerClientPtr client)
             goto cleanup;
         if (!(groupname = virGetGroupName(gid)))
             goto cleanup;
-        if (virAsprintf(&userid, "%d", (int)gid) < 0)
+        if (virAsprintf(&groupid, "%d", (int)gid) < 0)
             goto cleanup;
         if (virAsprintf(&processid, "%llu",
                         (unsigned long long)pid) < 0) {