NetDB: Fix usage of dbResponseTime stat

Actually update the stat for stores in dbStoreSent();
we are generally storing to different ffs than lookups, so we need the
stat for stores as well, since we use it as the timeout in StoreJob.

Change from 1-day to 1-hour stat.
Switch to avgOrLifetimeAvg() so the rate is always valid.
Reduce max time used for timeout.
This allows more peers to be tried before total timeout
Previously, the per-peer timeout was almost always the max.
Make sendStore() package private.
Javadocs and cleanups.