Pass lcb_t to map_error

This can be used to allow for more elaborate error handling schemes

Change-Id: Ic5a362f88be76e2bcd8a4e371809453afe07a487
Reviewed-on: http://review.couchbase.org/29928
Tested-by: Mark Nunberg <mnunberg@haskalah.org>
Reviewed-by: Sergey Avseyev <sergey.avseyev@gmail.com>