engine: Improving EventQueueMonitor for  RecoverySroragePool scenario

The following improvements will not allow to submitt a new events except of VDSCONNECTTOPOOL
during recovery process.
The current behaviour is good, but after chnage it will become much better

Change-Id: I06f1065db0dd017d1db5ea1dcbd5e8c983a6c46b
Signed-off-by: Michael Kublin <mkublin@redhat.com>