bitbake/runqueue: fix clash when setscene & real tasks done in same build

bitbake/runqueue: fix clash when setscene & real tasks done in same build

If a build causes a real task to be run when the setscene task has already
run then it was possible for dependent packages to be rebuilding at the same
time as a rebuild of the packages they depended on, resulting in failures
when files were missing. This change looks in the setscene covered list and
removes anything where a dependency of the real task is going to be run (e.g.
do_install is going to be run even though the setscene equivalent of
do_populate_sysroot has already been run).

As an additional safeguard we also delete the stamp file for the setscene
task under these circumstances.

Fixes [YOCTO #792]

(From Poky rev: b4268c08c350a7928a0b1a041b04ffe5a44e77b4)

Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>