cgm_destroy: ignore a NULL d->cgroup_path

Depending on where during container creation we failed, cgroup_path
may be NULL.  Don't try to delete the cgroup in that case.

(Also fix a wrong function name in an ERROR message)

Signed-off-by: Serge Hallyn <serge.hallyn@ubuntu.com>
Acked-by: Stéphane Graber <stgraber@ubuntu.com>
lxc-opensuse: Fix syntax error

Signed-off-by: Stéphane Graber <stgraber@ubuntu.com>