I can successfully start spring-boot with mvn spring-boot, the documentation mentions to gracefully exit the application hit ctrl-c.
I encountered same problem running SpringBoot application in eclipse on Mac. I manually had to find all the PID's using 8080 and kill them. But, fortunately, I realized that we can kill that tomcat instance right from the eclipse "console" view, by hitting the stop(Red square icon) button and run the spring boot application again.