NTP and other updates

• Add NTP_Server role to XIR
• Remove StartingIndex() modifier and revert to the prior way of naming ports by iterating over the NICs and ports of the owning xir.Resource
• Build MX python bindings with latest protobuf
• Add Vrf fields back to BGP configs when building facilities. These are needed by the portal to identify network fabrics (infranet vs xpnet) even though VRFs are not actually used anywhere