JCBC-400 : New feature test for credential encryption CRAM-MD5 or PLAIN

Change-Id: I003f5987f56392bd50b871e7a1eb4182008ccc2b
Reviewed-on: http://review.couchbase.org/32355
Reviewed-by: Michael Nitschinger <michael.nitschinger@couchbase.com>
Tested-by: Deepti Dawar <deepti.dawar@globallogic.com>