Add info log line in `getMonitorLock()`

When the monitor starts up and hangs on acquiring the monitor lock (for whatever reason, perhaps there's another monitor instance already holding the lock), there is no suggestion in the logs that the monitor is waiting on a lock. An info log would be appropriate here, along with a debug line for each failed attempt.

Ref: https://github.com/apache/accumulo/blob/master/server/monitor/src/main/java/org/apache/accumulo/monitor/Monitor.java#L601