Add force-stop support to launch script

Update the embedded launch script to support `force-stop`.

Closes gh-6223

spring-boot-integration-tests/spring-boot-launch-script-tests/src/test/java/org/springframework/boot/launchscript/SysVinitLaunchScriptIT.java

@@ -118,6 +118,14 @@ public class SysVinitLaunchScriptIT {
 				.has(coloredString(AnsiColor.YELLOW, "Not running (pidfile not found)"));
 	}
 
+	@Test
+	public void forceStopWhenStopped() throws Exception {
+		String output = doTest("force-stop-when-stopped.sh");
+		assertThat(output).contains("Status: 0");
+		assertThat(output)
+				.has(coloredString(AnsiColor.YELLOW, "Not running (pidfile not found)"));
+	}
+
 	@Test
 	public void startWhenStarted() throws Exception {
 		String output = doTest("start-when-started.sh");

spring-boot-integration-tests/spring-boot-launch-script-tests/src/test/resources/scripts/force-stop-when-stopped.sh

@@ -0,0 +1,4 @@
+source ./test-functions.sh
+install_service
+force_stop_service
+echo "Status: $?"

spring-boot-integration-tests/spring-boot-launch-script-tests/src/test/resources/scripts/test-functions.sh

@@ -21,6 +21,10 @@ stop_service() {
   service spring-boot-app stop
 }
 
+force_stop_service() {
+  service spring-boot-app force-stop
+}
+
 await_app() {
   if [ -z $1 ]
   then