Get rid of dead Makefile targets

There are no longer any tests left over that can be run on tox. All tests are
run as D-Bus tests. Remove similar coverage target.

Signed-off-by: mulhern <amulhern@redhat.com>

Makefile

@@ -4,14 +4,6 @@ TOX=tox
 lint:
 	$(TOX) -c tox.ini -e lint
 
-.PHONY: coverage
-coverage:
-	$(TOX) -c tox.ini -e coverage
-
-.PHONY: test
-test:
-	$(TOX) -c tox.ini -e test
-
 .PHONY: fmt
 fmt:
 	yapf --style pep8 --recursive --in-place check.py setup.py src tests