The patch proposes adding a new binding_index to the
NetworkDhcpAgentBinding table, with an additional Unique
Constraint that enforces a single <network_id, binding_index>
per network.
1. When a network is triggered to be auto-scheduled to DHCP
agents, the number of DHCP agents is constrained by
dhcp_agents_per_network in neutron.conf. This prevents
too many DHCP agents from being scheduled in the first place.
2. If users manually schedule a network to specific DHCP
agents, the binding_index increments to show the number of
DHCP agents hosting this network.
Co-Authored-By: Oleg Bondarev <obondarev@mirantis.com>
Change-Id: I1bc3f8b69c337f7c1cf7375509a0da61def9baf1
Closes-Bug: #1535554
69b3762dda