bitbake: bitbake-server/worker: Hide os.fork() deprecation warning
We're fairly careful in bitbake about how we handle fork() calls and believe our code
to be safe. The upstream deprecation warning is problematic as it can appear in log
output as a WARNING, breaking tests. It also tends to alarm users.
Hide the warning for now to avoids the test failures.
(Bitbake rev: c636bd629896f56e5f3d4030da3d1f130590afc6)
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>