Bug 1347123: Call _router_clear_external_gateway instead of _router_set_external_gateway at the time of router deletion

Change-Id: Id80531182b277cba9d032c11f9256c9a2924b370
Closes-Bug: 1347123
Clear the external gateway info with object instead of id

Fixes bug: 1347123

Change-Id: I9823fd9490577be57ff4e2b742818707aaac517a
bgp_xmpp_inetvpn_test moved to flaky test

Change-Id: Ic8b333d4189a0f126d84222b26e645adb0c4b679
loaded the default values in the configuration files
rebased and resubmitted
changes applied after rebasing with master in contrail_vrouter_agent replacing vnswad