procd: support term_timeout parameter

Expose "term_timeout" parameter in procd.sh to allow init scripts to
request a longer termination timeout.

This is required to fix FS#859 in a later commit.

Signed-off-by: Jo-Philipp Wich <jo@mein.io>

package/system/procd/files/procd.sh

@@ -213,7 +213,7 @@ _procd_set_param() {
 			json_add_string "" "$@"
 			json_close_array
 		;;
-		nice)
+		nice|term_timeout)
 			json_add_int "$type" "$1"
 		;;
 		reload_signal)