Descriptive log for onu activate failures.
Descriptive log for onu activate failures.

Onu activate may fail if the adapter tries to activate
an onu that is being activated.

Change-Id: I7f417e4e8824bd8f7280d8afdf8779efd817fc0a

opencord/voltha,opencord/voltha,opencord/voltha,opencord/voltha,opencord/voltha