Disable JspServlet's development mode by default

This commit switches off the auto-configured JspServlet's
development mode by default. Development mode is then switched on
when DevTools is on the class path.

Closes gh-7039

spring-boot-devtools/src/main/java/org/springframework/boot/devtools/env/DevToolsPropertyDefaultsPostProcessor.java

@@ -52,6 +52,7 @@ public class DevToolsPropertyDefaultsPostProcessor implements EnvironmentPostPro
 		properties.put("spring.resources.cache-period", "0");
 		properties.put("spring.template.provider.cache", "false");
 		properties.put("spring.mvc.log-resolved-exception", "true");
+		properties.put("server.jsp-servlet.init-parameters.development", "true");
 		PROPERTIES = Collections.unmodifiableMap(properties);
 	}