Make Neutron API name consistent

Previously several types of name are used for same type operations
in Neutron releated API method names.

* XXXX_modify -> XXXX_update
* <plural>_get -> <singular>_list
* <plural>_list -> <singular>_list

Closes-Bug: #1261283
Change-Id: I95c268822d1a55ea0440b44ea2c7993979ee4c36
Merge "Make Neutron API name consistent"