CCBC-346: bc_http: Handle failed connection scheduling

Change-Id: I99f29f1dfa187baf0cdd45efc4f90e4fda144d9e
Reviewed-on: http://review.couchbase.org/35005
Reviewed-by: Subhashni Balakrishnan <b.subhashni@gmail.com>
Tested-by: Mark Nunberg <mnunberg@haskalah.org>