VOLTHA DPID generation is not predictable and thus access device information can't be provisioned in ONOS

Currently VOTHA generates a DPID for an OLT based on two factors:
1. the vcore which is the master of the device
2. an incremental index for each vcore

As you cannot predict which vcore will be used when an OLT is connected, today you have to configure of:000100..1, of:000200..1, and of:0003...1, etc. in ONOS as the configuration for the first OLT. If the OLT comes up under vcore 1, the access device configuration of:000100..1 will be used.

The problem is that when the second device comes up, it will likely come up under vcore 2 or 3 and thus try to read the access device configuration of of:000200..1 or of:000300..1, which was already had to configured for the information for the first OLT.

In stead of generating DPIDs in this way, VOLTHA should generate, as per the OF spec*, so that it would be "more" possible to provide configuration to ONOS based on the DPID.

I would recommend that the top 16 bits continue to be used for the vcore identifier, but change voltha and the adapters to use the management MAC address of the switch (or equivalent unique, unmutable, hardware value) for the lower 48 bits.

• The datapath_id field uniquely identifies a datapath. The lower 48 bits are intended for the switch
  MAC address, while the top 16 bits are up to the implementer.