Oh, you wrote:
...but on the console i observed that the instance is actually getting the DHCP IP.
I assumed everything works as expected, so you say the instance is *NOT* getting an IP? Is DHCP enabled in the base image this instance is based on? Also check neutron dhcp logs for any errors that may occur during instance creation. Usually, the compute nodes also log some neutron related events like

Code:
Received unexpected event network-vif-plugged-4a2fc552-98af-41b3-a0a2-d6720e66a053 for instance
But as a first guess, I would go with the base image and check if DHCP is enabled.