Improve multi DHCP agent support

Since Grizzly release, a specific number of DHCP agents can be scheduled to host a
network.
This enables redundant DHCP agents for configured networks.

Change-Id: I3388282c0a46eafa2b4e0e6d2d0293fa91e46cc3
Signed-off-by: Emilien Macchi <emilien.macchi@enovance.com>
Merge "Improve multi DHCP agent support"