Hide pkg_install EOL warnings when testing

MFH
Use stage-qa now instead of our own symlink checking

MFH
Use check-sanity not check-config as its own phase.

Only set DEVELOPER during this phase to trigger warnings. We want to be
able to call stage-qa on our own, so don't set for other phases.

MFH
Disable DEVELOPER waits when running non-interactively

MFH
Only skip erroring on missing origins for -a for now

Discussed with:	antoine
Make missing category origin a warning