fix related to mx test failure when ran using contrail APIs:

1. adding route target while creating VN
2. added retry in si interface verification.sometime no interfaces will be up then it was giving error for None type object,fixed that too.
3. use FQ VN name when creating policy via contrail vnc.
4. update policy based on option passed in test case

Change-Id: I38aeabc3390fea7ebb4bdb17dbb0b63c5dd5a7c7
Merge "fix related to mx test failure when ran using contrail APIs:" into R2.0