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: 78ae96e667d3fbb8649fe25eb073e15a99d61cc8)
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>