Clear caches on initial restart

Tweak `Restarter` to clear caches on the initial restart.

See gh-3082

spring-boot-devtools/src/main/java/org/springframework/boot/devtools/restart/Restarter.java

@@ -157,6 +157,7 @@ public class Restarter {
 				@Override
 				public Void call() throws Exception {
 					start();
+					cleanupCaches();
 					return null;
 				}