When we execute work in a background thread we copy the logging context
to it and unset it before we return it to the thread pool. If we get a
thread from the pool that has a non-empty logging context this is
unexpected and we want to know about it.
Also add a clear() method to LoggingContext to make unsetting the
logging context easier.
Signed-off-by: Edwin Kempin <ekempin@google.com>
Change-Id: Ic40ce525f5f4508fe4eb56d78a704256a98b8e0c
b3369b566a