cgmanager: &existed for remove+create now returns -1 on failure

Signed-off-by: Serge Hallyn <serge.hallyn@ubuntu.com>
Revert "lxc-start: fix the container leak when daemonize"

This reverts commit c3f0f139e155f53c83e0a81f14094e9d0f40e8e9.

Done as Serge Hallyn's request:
 Nacked-by: Serge E. Hallyn <serge.hallyn@ubuntu.com>