Wrap logcat invocations with timeout.

We've seen evidence that the logcat binary can end up wedged, which
means we can eventually starve system_server for FDs.  To mitigate
this, wrap logcat using the timeout utility to kill and clean up if
it takes too long to exit.

Bug: 27994717, 28021719, 28009200
Change-Id: Ieed1460d89598628a5db868645fd305d0e9054ed