Revert "engine: Forbid Bootable and Shareable Disks"

This reverts commit 673e7b876b13650f5b5cec794486bfef1b0fd565.

Following the decision to allow disks to be both bootable and shareable
at the same time, this patch is no longer relevant.
(See the discussion at: https://bugzilla.redhat.com/1084103).

Change-Id: I6d8357e51e3c4364fd44754537150eb21d0acba4
Relates-To: https://bugzilla.redhat.com/1084103
Signed-off-by: Idan Shaby <ishaby@redhat.com>
core: Added Exec. Msg. for AddPosixFsStorageDomain

Added an execution message for AddPosixFsStorageDomain.

Change-Id: I1b2bdc2199988785dd37b8b9dcf361fbab387496
Bug-Url: https://bugzilla.redhat.com/1139169
Signed-off-by: Idan Shaby <ishaby@redhat.com>