fix mpd module hang after suspend

[bretello]

I've been having this annoying issue for a while, in which after waking up from a long suspend the MPD module is not updating anymore.

Clicking the MPD module icon does trigger play/pause events but it does not show the active song anymore.

I think I finally manage to track it down to a broken idle connection, and this PR fixes the issue.

How to reproduce

Run:

systemctl suspend

go get a beer, come back after a lot of time, and the MPD module will not update anymore.

If you don't have a lot of time, I managed to reproduce similar symptoms by killing the socket(s) using ss:

export MPD_HOST=<mpd host>
export MPD_PORT=<mpd port>
sudo ss -k "dst $MPD_HOST and dport $MPD_PORT" # WARNING: this will kill ALL connections to MPD_HOST:MPD_PORT

The mpd module will not update anymore, even though it responds to clicks.

[bretello]

I changed this (and below) to trace since they made debugging with -l debug very noisy. I'll be happy to revert this and/or open another PR in case we want separation of concerns.

[bretello]

Seems this is not fixing the issue, will keep investigating.

[bretello]

Update: this seemingly has to to with libmpdclient: running mpc idleloop shows the same problem after a long suspend. It looks like the underlying connection dies but the client never realizes this and keeps waiting for idle events.