rdbms: include client ID hash in ChronologyProtector cookies

rdbms: include client ID hash in ChronologyProtector cookies

Previously, if an internal service forwarded the cookies for a
user (e.g. for permissions) but not the User-Agent header or not
the IP address (e.g. XFF), ChronologyProtector could timeout
waiting for a matching writeIndex to appear for the wrong key.

The cookie now tethers the client to the key that holds the
DB positions from their last state-changing request.

Bug: T194403
Bug: T190082
Change-Id: I84f2cbea82532d911cdfed14644008894498813a