bosserver: Catch failures to create daemon thread

If we can't create the bozo daemon thread, then don't keep going
regardless. Just warn the user and exit.

Caught by coverity (#988414)

Reviewed-on: http://gerrit.openafs.org/9269
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
(cherry picked from commit 4587ddc130547b4cce723476cfa798a03ccc0320)

Change-Id: I4dcf67f4aeb2533ad39e9b1b0202d00205584118
Reviewed-on: http://gerrit.openafs.org/11011
Reviewed-by: Chas Williams - CONTRACTOR <chas@cmf.nrl.navy.mil>
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>