Use graduated oslo libraries

The following libraries have been graduated:
- gettextutils -> oslo.i18n
- jsonutils -> oslo.serialization
- strutils, timeutils -> oslo.utils

Add neutronclient.i18n module as oslo.i18n adapter.

Remove openstack.common related files completely
because neutronclient no longer use any oslo-incubator modules.

Closes-Bug: #1382017
Change-Id: Ib7ebcb691a12858049baab3b122f95bf43038f18
Merge "Use graduated oslo libraries"