Remove redundant code for getting error string

Change-Id: I6369a14895d71fed61e2a45fe8d9aa833374e631
Reviewed-on: http://review.couchbase.org/31658
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Filipe David Borba Manana <fdmanana@gmail.com>
Tested-by: Filipe David Borba Manana <fdmanana@gmail.com>