bitbake: runqueue/bitbake-worker: Fix dry run fakeroot issues
When using the dry run option (-n), bitbake would still try and fire
a specific fakeroot worker. This is doomed to failure since it might
well not have been built.
Add in some checks to prevent the failures.
[YOCTO #5367]
(Bitbake rev: f34d0606f87ce9dacadeb78bac35879b74f10559)
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>