libcgroup: Make the group change logs more readable

libcgroup: Make the group change logs more readable

From: Jan Safranek <jsafrane@redhat.com>

Function cgre_process_event() logs success/failure of group change two
times, each with different log severity. It should be logged just once.

[dhaval@linux.vnet.ibm.com: Minor changes to the changelog]
Signed-off-by: Jan Safranek <jsafrane@redhat.com>
Acked-by: Dhaval Giani <dhaval@linux.vnet.ibm.com>
git-svn-id: https://libcg.svn.sourceforge.net/svnroot/libcg/trunk@320 4f4bb910-9a46-0410-90c8-c897d4f1cd53