Always keep restarting k3s process by openrc

When for some reason, k3s crashes, and can't startup again, e.g. when
the data backend is not available (dqlite crashed, database server is
offline, ...), on openrc systems, supervise-daemon will try to restart
it, as per supervise-daemon(8):

    respawn-max:

    Sets the maximum number of times a daemon will be respawned during
    a respawn period. If a daemon dies more than this number of times
    during a respawn period, will give up trying to respawn it and exit.
    The default is 10, and 0 means unlimited.

Setting respawn-max to 0, makes sure a k3s process on openrc systems will
keep trying to come online, even if the database backend is offline for a
longer period of time.

This aligns the openrc service configuration with the systemd
configuration, which has

    Restart=always
    RestartSec=5s

install.sh

@@ -691,6 +691,7 @@ error_log=${LOG_FILE}
 
 pidfile="/var/run/${SYSTEM_NAME}.pid"
 respawn_delay=5
+respawn_max=0
 
 set -o allexport
 if [ -f /etc/environment ]; then source /etc/environment; fi