avahi: inherit python classes, use PACKAGECONFIG
Without using our python classes and having appropriate dependencies, the
build is nondeterministic, and whether a python-avahi package is produced will
vary depending on the host environment, yet avahi-discover is always produced,
and it depends on python-avahi.
(From OE-Core master rev:
4599ef630c13224506671bf84569bfc240cd3032)
Signed-off-by: Christopher Larson <chris_larson@mentor.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
