"proxy_address: None" during mib_reset.

Error in onu-adapter's log during multi ONUs bringup test:

_20190821T182828.071 ERROR MainThread omci_cc.send

{device_id: 9d32f647c0f890e1e00ce11b, omci_cc_enabled: True, *proxy_address: None*, tx_errors: 1, event: cannot-send-omci-msg, instance_id: a4fedcc0e230_1566412027, vcore_id: None}

_
_20190821T182828.072 ERROR MainThread mib_upload.perform_mib_upload

{name: MIB Upload Task, task_id: 13, device_id: 9d32f647c0f890e1e00ce11b, e: OMCI is not enabled, event: mib-upload, exception: Traceback (most recent call last):_ _File "/usr/local/lib/python2.7/dist-packages/pyvoltha/adapters/extensions/omci/tasks/mib_upload.py", line 99, in perform_mib_upload_ _results = yield device.omci_cc.send_mib_reset()_ _Exception: OMCI is not enabled, instance_id: a4fedcc0e230_1566412027, vcore_id: None}

_

While starting onu_device_entry, onu-adapter starts omci_cc, which queries getDevice from rw_core and sets omci_cc._proxy_addres with response. Meanwhile it starts state machine(with reactor.callLater) which tries to send mid_reset first.  Sometimes mibreset is attempted to send before the device response received from rw_core. So mibreset fails because the omci_cc._proxy_address is not still set. This occurs probably in the case getDevice response is delayed.