Remove pointless fetch timer

We already have a good mechanism in place for fetch thread timing, the
second layer of timing was just a way to waste time. At the cost of
taking feed_lock (a low contention lock) briefly once a second (instead
of once a minute) fetch work is done faster.

This is especially important on a fresh startup where there is no disk
presence already.

In addition, scale back some logging that is made annoying by the
increased frequency of some fetch calls.