libmemunreachable: fix long timeout on error

The collection thread should unblock the parent when it fails in order
to prevent a 100 second timeout delay.  Also reduce the timeout to 30
seconds, and fix a few log messages.

Bug: 27208635
Change-Id: I47f9ce4f645c453810fec57bef557c32a665eefb
(cherry picked from commit b1b7923e)