JSCBC-150: Correct getting nodes before cluster config available.

This caused segfaults when methods retrieving a hostname were
invoked before the bucket was connected.

Change-Id: Ia8faadf76297056c40bd41dadb32a2e4c90f83be
Reviewed-on: http://review.couchbase.org/41982
Reviewed-by: Mark Nunberg <mnunberg@haskalah.org>
Tested-by: Brett Lawson <brett19@gmail.com>