Fix LoggingApplicationListener

- If `logging.config` is set and could open/read the resource
then, return.
  - Currently, it logs warning though the resource is successfully
read.
`setLogLevels(system, environment);` is no longer called if you put a `return` here.  See https://github.com/ilayaperumalg/spring-boot/blob/logging-application-listener/spring-boot/src/main/java/org/springframework/boot/logging/LoggingApplicationListener.java#L203

Should the warning be in the catch block instead?