Make svc_static_route_intergration_test more robust

Add task_util::TaskSchedulerLock to stop+drain and start scheduler.
Use TaskSchedulerLock when verifying paths for service chain route.

Change-Id: I641eeaf4c3bcac7c44232c532dea07874f0e48e5
Add SessionDown tests to bgp_xmpp_rtarget_test

Change-Id: I630d49570f7770db4184764b7797f9fa8de61b26
Increase priority of routes by LINK_LOCAL_PEER.

Fixes bug where path added by ARP is of higher priority than link-local path.
This was resulting in failing of metadata access to/from VM

Change-Id: I99af613fe02ad55aab5f0921cb67fc44d77fee87
Partial-Bug: #1364308
Fix errors in test_linklocal

Change-Id: I1079a12e5929bee0d38116ef857e442707beccac
Merge "Add SessionDown tests to bgp_xmpp_rtarget_test"
Merge "Increase priority of routes by LINK_LOCAL_PEER."
Merge "Make svc_static_route_intergration_test more robust"