staging: Fix overlapping file failures

If there are different providers of a file and they are swiched when the
recipe isn't machine specific, we can get tracebacks due to the overlapping
files. The issue is that the previous provider isn't uninstalled since
the system can't tell whether some later task needs them.

By tracking which tasks we depend upon, the code can now choose to
uninstall more things since a later task can reinstall if/as needed.

The code here was to protect against code with two different tasks
running in parallel which is still protected agaisnt.

[YOCTO #13702]

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
Signed-off-by: Steve Sakoman <steve@sakoman.com>