Add a timeout option to client commands

[aquette]

upsc, upscmd and upsrw should provide a -t timeout option.
Underlying mechanism is already available in libupsclient->upscli_tryconnect(...).

Alioth patch #313881
https://alioth.debian.org/tracker/index.php?func=detail&aid=313881&group_id=30602&atid=411544

An external contributor (Imene Guerfa) is already working on this.

[cnaslain]

I run upsc as an healthcheck command and sometime; it never returns and the number of ghosts process increases indefinitely.
Having a timeout option would be great to fail the upsc command if it does not returns in time.

Running Network UPS Tools upsc 2.8.2 in docker with upsc ups-montcalm@localhost 2>&1 | grep stale -c && exit 1 || exit 0 healthcheck command.