CCBC-358: restore lcb_get_host/lcb_get_port to return proper info

This would not always return valid information if there was no current
active REST provider. This tries fairly hard to grab a proper host/port
to be used as a REST endpoint

Change-Id: Ic6a26b1fa721812da13ecb7d6b79a2502aed556a
Reviewed-on: http://review.couchbase.org/35382
Tested-by: Mark Nunberg <mnunberg@haskalah.org>
Reviewed-by: Sergey Avseyev <sergey.avseyev@gmail.com>