AdapterProperties: change log level and wording

* When state transition goes from CONNECTED to DISCONNECTED or
  from DISCONNECTED to CONNECTED, it is abnormal, but still falls into
  some normal use case such as sudden disconnection
* This CL changes the log level to warning and reword it to "abnormal"

Bug: 65591907
Test: make, no functional change
Change-Id: I90b801281dde6c5a5c349568dc8e0c4a740b4db6