ceph: handle CephCluster stopCleanupCh better
ceph: handle CephCluster stopCleanupCh better

Investigate a possible memory leak around CephCluster cleanup's
stopCleanupCh channel. Add more close() statements and comment that Go's
garbage collector is able to close the channel when there are no more
referents to the channel.

Signed-off-by: Blaine Gardner <135b86f2968bdbcc730c10d8ababd343bb675986@redhat.com>

rook/nfs,rook/nfs,rook/rook,rook/rook,rook/rook,rook/rook,rook/nfs,rook/rook