Support for same OF port Name across different DPN

Support for same OF port Name across different DPN

Description: Dpnid is prefixed to the Parent Inte-
-rfaces(<dpnid>:<interfacename>) in the Interface
State Operational DS, that fixes issue of,if two
compute nodes are managed by a single ODL and both
define "eth1" as the interface for external
network, their entries will overlap and the
interface-state subtree will contain only one
entry.

Change-Id: I2bf4f4462d9b440e86523f15f3770aecd4059799
Signed-off-by: echegow <chetan.arakere.gowdru@ericsson.com>