Allow '0X' as valid hex representation for extra dhcp options.
Allow '0X' as valid hex representation for extra dhcp options.

Some of test cases extra dhcp options provide
hex value with '0X' so to allow this we will allow
both '0x' and '0X' as a valid hex representation.

Change-Id: I32124f12f841c4bccb14220e9611065a5a3aef71

naveensan1/nuage-openstack-neutron,nuagenetworks/nuage-openstack-neutron,naveensan1/nuage-openstack-neutron,nuagenetworks/nuage-openstack-neutron