Attempt to run couple of evpn cases faster

Do VNFixture validation before VMs are booted
Better to wait for the dhcp server to be up before other VMs fetch
IPs from it
Better to do verify_on_setup() before waiting for ssh on the vms

Change-Id: I94ec9fe3889da3a2a482c98625615c3a7dfb4c3c
Merge "Attempt to run couple of evpn cases faster"