engine: Correlation id was not send to host - fixing it

The following patch should fix a bug with correlation id, which was not
send to vdsm.
In order to send it a correlation id should be kept inside internal
callable.

Change-Id: I45867ee8aea7a69ab9025a2ab2301d7cb9d74663
Bug-Url: https://bugzilla.redhat.com/844335
Signed-off-by: Michael Kublin <mkublin@redhat.com>
Signed-off-by: Yaniv Bronhaim <ybronhei@redhat.com>