fixes #1772 @2.5h

Conflicts:

	src/knot/server/tcp-handler.c
	src/knot/server/xfr-handler.c
	src/knot/server/zones.c
	src/libknot/nameserver/name-server.c
	src/libknot/updates/xfr-in.c
	src/tests/libknot/libknot/response_tests.c