common: format Throttle test to 80 columns

Signed-off-by: Loic Dachary <loic@dachary.org>
common: fix rare race condition in Throttle unit tests

The thread created to test Throttle race conditions updates a value (
throttle.get_current() ) that is tested by the main gtest thread but is
not protected by a lock. Instead of adding a lock, the main thread tests
the value after pthread_join() on the child thread.

http://tracker.ceph.com/issues/6679 fixes #6679

Signed-off-by: Loic Dachary <loic@dachary.org>
Merge pull request #944 from dachary/wip-6679

common: fix rare race condition in Throttle unit tests

Reviewed-by: Sage Weil <sage@inktank.com>