core: fix interfaces initialization for VM object

In the constructor of VM object we always set the interfaces to empty
list. It is redundant as we get VmStatic object which is initialized
with empty list. The problem with the redundant setting is that even if
passing VmStatic instance initialized with interfaces, we were override
it. Thus, this setting is removed.

Change-Id: I4537f48ecfd7f3a42e96e345c24f085105361e02
Signed-off-by: Arik Hadas <ahadas@redhat.com>