bc_http: remove 'protocol_error' handling

We shouldn't fail out an entire provider if a single node happens to
complain about something

Change-Id: If16ce998f43c75ddbcfa7dc92f7fd61ebdad72b5
Reviewed-on: http://review.couchbase.org/34954
Reviewed-by: Brett Lawson <brett19@gmail.com>
Tested-by: Mark Nunberg <mnunberg@haskalah.org>