Avoid unnecessary WaitConditionLoop delays in ChronologyProtector

Avoid unnecessary WaitConditionLoop delays in ChronologyProtector

Since it takes time for the agent to get the response and set the
cookie and, as well, the time into a request that a LoadBalancer is
initialized varies by many seconds (cookies loaded from the start),
give the cookie a much lower TTL than the DB positions in the stash.

This avoids having to wait for a position with a given cpPosIndex
value, when the position already expired from the store, which is
a waste of time.

Also include the timestamp in "cpPosIndex" cookies to implement
logical expiration in case clients do not expire them correctly.

Bug: T194403
Bug: T190082
Change-Id: I97d8f108dec59c5ccead66432a097cda8ef4a178