Add more estimation modes to pendingWriteQueryDuration()

Add more estimation modes to pendingWriteQueryDuration()

* Use this to exclude some common cases of harmless queries that
  happen to block on row-level locks for a long time. This does
  not apply to UPDATE/DELETE however, due to the ambiguity of
  time spent scanning vs locking.
* Update commitMasterChanges() and JobRunner to use the new
  mode to avoid pointless rollback or lag checks.

Change-Id: Ifc2743f2d8cd109840c45cda5028fbb4df55d231