core: MoveVmCommand storage allocation

This patch is a part of a series of patches, fixing storage allocation
validations throughout the system.
In this patch MoveVmCommand is now using correct validations - as they
were already implemented in the superclass MoveOrCopyTemplateCommand.

Change-Id: I9d0600d21573cae4ef278a4c0951724449e4eded
Signed-off-by: Vered Volansky <vvolansk@redhat.com>
core: Removed redundant tests

After the refactoring of storage allocation there's no longer need for
tests of the 'old' verifications in StorageDomainValidatorTest.
Removed.

Change-Id: I5270d2ee1c1a567f61ab9813ffe2d223e062d8a0
Signed-off-by: Vered Volansky <vvolansk@redhat.com>