Treat freeswitch-{sounds,music} as virtual packages only

Previously we were creating freeswitch-music, freeswitch-sounds,
freeswitch-sounds-en, and freeswitch-sounds-en-us metapackages and
also providing those names as virtual packages from the
freeswitch-{sounds,music} source packages.  This is unnecessarily
confusing and meant that freeswitch-all wasn't depending on any sounds
in actuality as it was also providing freeswitch-sounds.