Make a shutdown timeout configurable for sysv

[annamel]

sysv code has a shutdown timeout equal to 10
if is_running; then echo -n "Stopping $name.." kill $(get_pid) for i in $(seq 1 10) do if ! is_running; then break fi echo -n "." sleep 1 done
If the service hasn't completed within 10 seconds, restart fails (stops fails 'cause of is_running is true and 10 1-seconds long intervals have exhausted; start fails since is_running is true; meanwhile the service completes).

The absence of configurable timeouts make it complicated to use kardianos.service for http.Server with graceful shutdown. 'Cause graceful shutdown timeout actually must be below this hardcoded 10 seconds period.

[kardianos]

I understand. Feel free to propose a change/PR. This change makes sense.