core: [Fix] Check PCI limits when adding NICs

The AddVmInterfaceCommand didn't account for all the existing NICs
while passing the "interfaces" list to the checkPciAndIdeLimits
procedure, so a limitless number of NICs could be created.
This change fix this behaviour (like in the UpdateVmInterfaceCommand).

Change-Id: Ib8594848b576dd5543d0fa77b5471b5dadc6ac4d
Signed-off-by: Gustavo Pedrosa <gustavo.pedrosa@eldorado.org.br>