Iface: disallow network tuning in session mode globally

Patch 43b67f2e disallowed network tuning only with qemu driver, however
this patch moved the check for root privileges into
virNetDevBandwidthSet function, so the call should now
fail in all possible cases. A mock function was created so that the test
suite doesn't fail because of unsufficient privileges.

tests/virnetdevbandwidthmock.c

@@ -0,0 +1,28 @@
+/*
+ * Copyright (C) 2014 Red Hat, Inc.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library.  If not, see
+ * <http://www.gnu.org/licenses/>.
+ *
+ * Author: Erik Skultety <eskultet@redhat.com>
+ */
+
+#include <config.h>
+#include <unistd.h>
+#include <sys/types.h>
+
+uid_t geteuid(void)
+{
+    return 0;
+}