logd: clearAll by UID speedup

(cherry pick from commit 2b25c660)

- If doing a clear, skip accounting
- Ensure for busy checking, behind a region lock for instance, only
  break out if there was something to do. Basically move the filter
  actions first, and defer checking the region lock to the ends of
  the loops.

Bug: 23711431
Change-Id: Icc984f406880633516fb17dda84188a30d092e01