floss: Increase logging in btmanagerd

Move the state machine logger to INFO and log when start/stop is
a no-op. Also change some important notifications to WARN so that they
will show up in syslog more clearly.

Bug: 296617922
Test: mma -j
Test: Load on ChromeOS and check logs
Change-Id: I09b3f16d44dbb4a32663a4ff2b01eda7e8afc140