JCBC-282 Two tests added for connection refused and network un-reachable.

Change-Id: I6bab9dd16a9804bfd4232c1433fc186028300703
Reviewed-on: http://review.couchbase.org/25563
Reviewed-by: Matt Ingenthron <matt@couchbase.com>
Tested-by: Deepti Dawar <deepti.dawar@globallogic.com>