core: fix virtio-scsi validation on update VM

Fix VirtIO-SCSI validation when updating a running VM:
* Added a new signature for vmDeviceChanged method which
  gets also a specific VmDeviceType.
** Needed for using getVmDeviceByVmIdTypeAndDevice
   method from VmDeviceDao. I.e. instead of fetching
   all devices of VmDeviceGeneralType.CONTROLLER,
   filter also by VmDeviceType.VIRTIOSCSI specifically.
* Added new test-cases for updating a running VM.

Change-Id: I6f2247319b014f59d5c19c0054ee9e63d1dfe204
Bug-Url: https://bugzilla.redhat.com/1058295
Signed-off-by: Daniel Erez <derez@redhat.com>