Remove the "found_available_arg" variable from depgraph._select_pkg() and use

Remove the "found_available_arg" variable from depgraph._select_pkg() and use
the "matched_packages" variable instead. This solve a problem where the
"found_available_arg" flag is unreliable due to the slot filtering behavior
of depgraph._iter_atoms_for_pkg(). For example, a higher version in a
different slot than the available ebuild might be masked or unavailable, and
depgraph._iter_atoms_for_pkg() will not identify the available ebuild as
a match due to this installed package (which is not available for reinstall).

svn path=/main/trunk/; revision=11702