macfuse 4.x turns out to be incompatible with the old mounting method where
you open the device by yourself and only supports the newer method where you
receive a file descriptor from `mount_macfuse` through a unix socket.
when user mount via fstab, we get '-o rw' implicitly, and under
directmount this _enabled_ MS_RDONLY, which is the opposite of what we
want
refs https://github.com/kahing/goofys/issues/483
Vitaliy Filippov
Michael Stapelberg