NEC plugin: Remove a colon from binding:profile key due to XML problem

NEC plugin: Remove a colon from binding:profile key due to XML problem

In XML specification, if a tag name contains a colon, a part before
a colon is interpreted as namespace. If key names in binding:profile
dict contains a colon, Neutron XML serializer sends them as-is.
A colon in key names should be used only if XML namespace are used.
NEC plugin uses a colon in key names and it leads to failures to XML
deserialization. To avoid this problem, this commit removes a colon
and prefix n key names in port binding:profile so that client XML
deserializer decodes XML response successfully.

Change-Id: Ie32a2417bbce03bfc6e8f7907c0b4090fbc9e7b6
Closes-Bug: #1294166