PYCBC-106: Expose server list

Change-Id: Icf0b466e088315d9b95fe10e8a5ed15c3dbe35af
Reviewed-on: http://review.couchbase.org/26281
Reviewed-by: Volker Mische <volker.mische@gmail.com>
Reviewed-by: Mordechai Nunberg <mnunberg@haskalah.org>
Tested-by: Mordechai Nunberg <mnunberg@haskalah.org>