--tray option does not hesitate to fill up systray

[fezboy]

Above is an obviously contrived example, but while editing and reloading my i3 config i get a bunch of tray icons ~~and stray udiskie processes, which don't go away when you use the tray icon's "quit" option.~~¹ I know I could solve this by changing my i3 config from exec_always to exec, but letting people run multiple udiskie processes at once seems like a bad idea. (I don't see why you would need or want more than one)

Edits:

1. Yes they do I just can't count

[coldfix]

Hey,

true. I don't think it's a huge problem, since launching multiple udiskie instances can easily be avoided on the user side, but I'm nevertheless open to adding a single-instance lock that will prevent this behaviour by default, but it will take me some time to get to that.

For future me or anyone who wants to contribute a PR on this: Examples for how to do that can be found in https://stackoverflow.com/questions/380870/make-sure-only-a-single-instance-of-a-program-is-running. I think shipping a small function similar to the one in single_process might be best. It should be possible to bypass the single-instance check using a command line option --no-single-instance or similar, in case someone relies on multiple instances for one reason or the other.