engine: Preventing running host monitor during activation of host operation

The following patch will prevent running of host monitoring during Activate host operation.
It is means that activate host operation will wait untill monitoring will be finished and will acquire a lock.
When a lock is acquired by activate operation a monitoring will be skipped.

Change-Id: If7f5eed741ca392ed7144934c539d2aa70744431
Signed-off-by: Michael Kublin <mkublin@redhat.com>