ScheduledReporter reports metrics when stopped/closed even when not started

[ummels]

ScheduledReporter's close method calls its stop method, which calls report to report the metrics "one last time". This also happens if start has never been called.

In a SpringBoot application that registers a ScheduledReporter as a bean, this can lead to strange behavior since the start method is not automatically called by Spring Boot (because it has arguments which Spring Boot cannot infer), but close or stop is.