Add pylint tox environment and disable all existing warnings

pylintrc update disables all warnings that currently trigger on neutron
code.  The rough plan is to slowly re-enable warning categories as we
clean up code in question.

This change also includes a few ultra-trivial syntax cleanups where it
allowed the check to be immediately enabled for the rest of the
codebase:

- Added missing trailing newlines in several files
  (db/migration/__init__.py, nuage/{nuagedb,syncmanager,common/config}.py)
- Renamed self to cls in @classmethods
  (cisco/db/l3/device_handling_db.py)
- Removed whitespace around '=' in a kwarg
  (cisco/db/l3/device_handling_db.py, cisco/db/n1kv_db_v2.py)
- Updated deprecated pylint 'disable-msg' directive to newer 'disable'
  (cisco/extensions/qos.py)
- File-specific disable for too-many-format-args pending further
  investigation of alternatives
  (ml2/drivers/arista/arista_l3_driver.py)
- Import module rather than object and avoid long line
  (services/l3_router/l3_arista.py)

Change-Id: Ifb0a1a38e33f9073a78658ca578fbd2a42747724
Merge "Add pylint tox environment and disable all existing warnings"