bitbake: runqueue: Handle missing sstate dependencies better

bitbake: runqueue: Handle missing sstate dependencies better

If you "bitbake glibc-locale" then delete the libpcre-native sstate
and "bitbake glibc-locale -C package_write_rpm", it will fail with
rpmbuild missing the libprce library.

The reason is that libpcre-native fails to install from sstate (since
it isn't present) but doesn't get built and hence rpm-native tries to
run without its dependencies.

The simplest fix is not to add "covered" tasks which have failed to
install sstate. I can't help feeling there is more to this issue but
this does fix the current problem and shouldn't have adverse affects.
It is an unusual situation to have missing dependencies in sstate since
they're usually all present or not at all.

I've taken the opportunity to remove some old cruft from when we had
numeric task ids, the code can be simpler now.

(Bitbake rev: ba566b46d530b495f12f3a74f76434717b22a020)

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