Fix some possible warning messages during download parsing
Update the WIP pbi-manager for 10, fix some issues building / staging
the files after installing from PKGNG.
Don't remove the header-dir, since it gets bundled into the PBI now

Speed up the cleanup as well, don't need to do a rm -rf on STAGEDIR,
let the parent process do the cleanup as apart of the chroot. Also
more often than not it will be a ZFS dataset which we can more quickly
just destroy.