BUG 2344 : Refactor Clustering integration tests

Deploy the 3-node cluster using deploy script and then run the scripts like so

pybot -v MEMBER1:10.194.126.49 -v MEMBER2:10.194.126.50 -v MEMBER3:10.194.126.51 -v PORT:8181 -v USERNAME:root -v PASSWORD:cvg123 -v KARAF_HOME:/root/deploy/current/odl ./datastore
pybot -v MEMBER1:10.194.126.49 -v MEMBER2:10.194.126.50 -v MEMBER3:10.194.126.51 -v PORT:8181 -v USERNAME:root -v PASSWORD:cvg123 -v KARAF_HOME:/root/deploy/current/odl ./routedrpc

Change-Id: I4582a94ea22f40a9236de330ac80727b2d1d4094
Signed-off-by: Moiz Raja <moraja@cisco.com>
(cherry picked from commit b951cf5effb7d4b2dcecb99275111e6d42d5f115)