Fixed up SpringPlugin to handle Spring 5 changes

[TerminaCoder]

When I added javaagent argument to be spring-loaded 1.3 on springboot 2.x, I get the following error - Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is java.lang.IllegalStateException: Ambiguous handler methods mapped for , this code can Fixed up SpringPlugin to handle Spring 5 changes