webadmin: Added overloaded methods for RunMultipleActions()

The overloaded methods accept only one VdcActionType, and run it
multiple times. It also accepts a single callback, to be executed
after all similar actions have returned successfully.

Also changed the original RunMultipleActions() to accept List rather
than ArrayList (it shouldn't care about the implementation).

Change-Id: Ifbe1f99f72238714028b7f7762d67109559c473e
Signed-off-by: Lior Vernia <lvernia@redhat.com>