Fix log files not working in daemon mode, update some dependencies and silence poll interrupted error

[MemoryLeak55]

I added the ability to the cli to set pid files, useful for systemd units. I added the ability to set a working dir, and updated daemonize and tracing to the latest versions. Logging to files now work in daemon mode, as well as no complaints from epoll about being interrupted

[kennytm]

The _guard and thus log file will be dropped at the end of this branch. The _guard must be held at the top level in order for the log to keep working, i.e.

fn main() {
    ...
    let _guard;
    ...

                let (non_blocking, guard) = tracing_appender::non_blocking(log_file);
                _guard = guard;

    ...

this is basically the approach in the main branch

boringtun/boringtun-cli/src/main.rs

Lines 103 to 113 in f672bb6

	let _guard;
	if background {
	let log = matches.value_of("log").unwrap();
	let log_file =
	File::create(log).unwrap_or_else(|_| panic!("Could not create log file {}", log));
	let (non_blocking, guard) = tracing_appender::non_blocking(log_file);
	_guard = guard;