core: WARNING when failed to create OVF Store

Changed audit log severity to WARNING to indicate that there's a problem
here.

Change-Id: I78171fd1890435c9f98efec88496e81e5f84b9ce
Bug-Url: https://bugzilla.redhat.com/1134371
Signed-off-by: Allon Mureinik <amureini@redhat.com>
core: extract constant from HibernateVmCommand

META_DATA_SIZE_IN_BYTES was extracted to MemoryUtils due to use in
several vm related commands, as well as need for it in another command
in bz1119022 fix.

Change-Id: I1604cf4a82e3e202093acdab97939427ab335169
Bug-Url: https://bugzilla.redhat.com/1119022
Signed-off-by: Vered Volansky <vvolansk@redhat.com>
core: Use correct validation for SD selection

When creating a snapshot, use new storage allocation validations for
the vm volumes when selecting a domain. Some code has been removed as a
result from this change.

Change-Id: Iac901a638358b9b08bcc6992d783a42cbfcd9bfa
Bug-Url: https://bugzilla.redhat.com/1119022
Signed-off-by: Vered Volansky <vvolansk@redhat.com>