JCBC-325: Adapt Testcase to work with only one server.

The % 2 assertion on available servers is not needed (anymore)
and can lead to false negatives on unit test runs with only
one target server in the cluster.

Change-Id: I92f9edb8f5f9f9b7b4f3297a0f7576543840a9f5
Reviewed-on: http://review.couchbase.org/27608
Tested-by: Michael Nitschinger <michael.nitschinger@couchbase.com>
Reviewed-by: Deepti Dawar <deepti.dawar@globallogic.com>