CLOUDSTACK-4473: allow_egress referenced before assignment

When deploying with networkids allow_egress gets no default value. This
is a regression caused by fix for CLOUDSTACK-4418

Signed-off-by: Prasanna Santhanam <tsp@apache.org>
(cherry picked from commit 239ba9447109412cf48cfefc547d6b5fef83a4a9)

tools/marvin/marvin/integration/lib/base.py

@@ -344,8 +344,10 @@ class VirtualMachine:
 
         if networkids:
             cmd.networkids = networkids
+            allow_egress = False
         elif "networkids" in services:
             cmd.networkids = services["networkids"]
+            allow_egress = False
         else:
             # When no networkids are passed, network
             # is created using the "defaultOfferingWithSourceNAT"