net-dns/rbldnsd: drop the python-2.7 test suite.

net-dns/rbldnsd: drop the python-2.7 test suite.

The test suite for rbldnsd uses python-2.7 (only), and realistically
that's not going to change any time soon. This commit drops the test
suite from the ebuild so that the python team isn't blocked on me at
some later point. If upstream ever migrates the test suite to
python-3.x and makes a release, I can put it back easy enough.

Bug: https://bugs.gentoo.org/715180
Package-Manager: Portage-2.3.89, Repoman-2.3.20
Signed-off-by: Michael Orlitzky <mjo@gentoo.org>