Revert/rewrite of r40696.

Revert/rewrite of r40696.
* We used to have parameters to ignore errors, but they're obsolete now that we have exceptions. Implemented ES master failover using exceptions instead.
* Changing the number of DB connection attempts from 3 to 2 for some random getConnection() calls is almost pointless, adds lots of ugly formal parameters all of the place, and misses the big picture. It should be 2 by default, based on the original rationale. Any reasonable implementation of failover should have zero timeouts per request, by storing state. Changed the default to 2, or 1 if a long timeout is set.