Resend SIGTERM if app is still running 30 seconds after first attempt

Previously, the default launch script would send SIGTERM once and then
wait for up to 60 seconds for the app to have stopped. If the service
was stopped immediately after being started the first SIGTERM would
occasionally be ignored (presumably because the JVM was not yet in a
state to handle it) causing the service stop request to fail.

This commit updates the launch script to resend SIGTERM to the process
if it's still running 30 seconds after the first SIGTERM was sent.

Closes gh-4941

spring-boot-tools/spring-boot-loader-tools/src/main/resources/org/springframework/boot/loader/tools/launch.script

@@ -182,8 +182,9 @@ stop() {
 
 do_stop() {
   kill "$1" &> /dev/null || { echoRed "Unable to kill process $1"; return 1; }
-  for _ in $(seq 1 60); do
+  for i in $(seq 1 60); do
     isRunning "$1" || { echoGreen "Stopped [$1]"; rm -f "$2"; return 0; }
+    [[ $i -eq 30 ]] && kill "$1" &> /dev/null
     sleep 1
   done
   echoRed "Unable to kill process $1";