Only include couchbase_version after setting up sys.path

Change-Id: I8d0c79dd5bb7f8f67d3c7920e727789899864b19
Reviewed-on: http://review.couchbase.org/27399
Tested-by: Mordechai Nunberg <mnunberg@haskalah.org>
Reviewed-by: Volker Mische <volker.mische@gmail.com>