L3vpn test update

L3vpn test update

Additional configuration is necessary due
to policy changes in bgpcep implementation.

BGP policies require route target argument in
order for application peer to distribute routes
back to internal bgp peer. So we have to first
send route containg route-target argument from
ibgp, and then we can send l3vpn route to app
peer so it can identify ibgp as appropriate
for advertizement of such route.

Switched from using exabgp to play.py for sending
route from internal peer to application peer in
odl versions fluorine and further.

Change-Id: Id3570b421491a8c906f3e848fef6922d6812e07c
Signed-off-by: Tomas Markovic <tomas.markovic@pantheon.tech>