panic!() in Filesystem::init() will hang the FS stack

[cfstras]

I've discovered this by mistake, by having an unwrap() fail in my implementation of init().

As soon as this happens, some bad things occur:

• The process running the mount will hang indefinitely
• Any process that touches the mountpoint will completely hang (not even terminal output for Ctrl+C etc is shown anymore)
  • examples: mount prints every mount up until the fuse line, then hangs
  • anything else, such as ls will hang as soon as it encounters the mount
• kill -9 (nor any other kill) seems to help
• pkill -9 macfuse kills the process, but it just gets restarted
• At some point, the whole macOS system will start hanging and become unresponsive (I guess some queue somewhere gets full?)

Workaround: Don't do any work that can panic!() in main?