core: LSM - validate identical source and dest SDs

LiveMigrateVmDisksCommand:
Added a canDo validation for identical source and destination
storage domain IDs.

Change-Id: I75fbc21b654a10cd1207a70b437df75df971717e
Bug-Url: https://bugzilla.redhat.com/1103499
Signed-off-by: Daniel Erez <derez@redhat.com>