tests/functional: Bump config versions to 3.5

Signed-off-by: Gergely Nagy <algernon@balabit.hu>
travis: Don't install syslog-ng before make check

make check should work even when syslog-ng is uninstalled, so lets
test this property too, by not installing it.

Signed-off-by: Gergely Nagy <algernon@balabit.hu>