Test Disable and Enable ONU scenario for ATT workflow failing

The functional test "Test Disable and Enable ONU scenario for ATT workflow" occasionally fails when run with BBSim.  The ONU's UNI port remains in disabled state after the ONU itself is re-enabled.  The ONU sends a UniLinkUp alarm when it is enabled, but this alarm is not processed by the openonu-adapter.  The alarm is what is supposed to trigger the adapter to enable the UNI port.

The problem is that BBSim is providing a canned response to the queries made by the alarm resync task in the openonu-adapter.  This runs asynchronously every three minutes.  BBSim responds to the task that there are no outstanding alarms, and so the task clears the LanLossOfSignal alarm on the UNI port.  However, since the ONU is in DISABLED state, no further actions are taken.  Then the subsequent UniLinkUp alarm is ignored because there is not outstanding LanLossOfSignal alarm.

To reproduce this issue:

• Turn on DEBUG mode for openonu-adapter
• Disable BBSim ONU
• Wait for perform-alarm-resync in openonu-adapter logs
• Enable BBSim ONU.  The ONU will move to ENABLED state but its UNI port will still be DISABLED.