rgw/s3select : fix for error flow.

rgw/s3select : fix for error flow.
in some cases the error message does not return to client, connection got broken (invalid chunk length)
fix another broken connection
all data-source to use same API for sending error-response
add the option rgw_s3select_disable(boolean). upon turning-on this option, it rejects s3select-requests with an error-message
editorial.
rollback to ceph-master. the ceph/s3-tests#561 must be merged with ceph-PR

Signed-off-by: Gal Salomon <gal.salomon@gmail.com>
(cherry picked from commit 53ad57c9d4c18e369128f9e0f3a143f5608b56f9)