modem/rmtfs: upgrade to 0.2_git20210408, start before oFono/MM
At the moment, oFono/MM are usually stopped after rmtfs on shutdown. This does not make sense, since the modem managed by oFono/MM will disappear once rmtfs is stopped. Add a "before ofono modemmanager" to make sure that OpenRC will stop oFono/MM before rmtfs on shutdown.
This may or may not fix some occasional hangs during shutdown, but it definitely makes it possible for oFono/MM to shutdown cleanly.