engine: Changing CDA error message in GetDiskAlignmentCommand

When volume format is other than RAW alignment scan can't run when VM is
running because they can interfere with each other. The CDA message
needs to reflect better this information to the user.

Change-Id: I2b5aa44b309736ae761a65037406eeb6c5d6ba86
Bug-Url: https://bugzilla.redhat.com/1006402
Signed-off-by: Sergey Gotliv <sgotliv@redhat.com>