engine:VDSM errors code for hooks updated

Synced the VDSM error codes handled in engine
as per patch http://gerrit.ovirt.org/#/c/9671/

Removed reference to HookAlreadyEnabled and
HookAlreadyDisabled errors as vdsm does not
return these error codes anymore.

Change-Id: I2eb4e93c42758284e03a77a718d42edbe923327e
Signed-off-by: Sahina Bose <sabose@redhat.com>
Signed-off-by: Shireesh Anjal <sanjal@redhat.com>