CBQE-1032: use ejectNode ( forceEject ) in teardown

instead of rebalance out to clean up the node by testrunner param forceEject=False( by default)

adapted for xdcr/bacetestcase

Change-Id: Iedad7a90abfd447615d2f638e1ed92ad0d7cdd55
Reviewed-on: http://review.couchbase.org/24864
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Andrei Baranouski <andrei.baranouski@gmail.com>