CLOUDSTACK-4144: Add free vlan to shared network in TestVMLifeCycleSharedNwVPC

Shared network has to have specifyVlan = True. So changed it to True
and aded a function to get free vlan.

Signed-off-by: Prasanna Santhanam <tsp@apache.org>
local storage is not enabled on the zone

Signed-off-by: Prasanna Santhanam <tsp@apache.org>