https://bugzilla.redhat.com/show_bug.cgi?id=1245476

We won't return the errno after commit 0d7f45ae, and
the more clearly error will be set in the code in vircgroup*.
Also We will always report error "Operation not permitted",
because the return is -1.
Signed-off-by: NLuyao Huang <lhuang@redhat.com>