python: Fix several pep8 whitespace errors.

python: Fix several pep8 whitespace errors.

Fix the following pep8 errors:

  E201 whitespace after '('
  E203 whitespace before ','
  E222 multiple spaces after operator
  E225 missing whitespace around operator
  E226 missing whitespace around arithmetic operator
  E231 missing whitespace after ':'
  E241 multiple spaces after ':'
  E251 unexpected spaces around keyword / parameter equals
  E261 at least two spaces before inline comment
  E262 inline comment should start with '# '
  E265 block comment should start with '# '
  E271 multiple spaces after keyword

Signed-off-by: Russell Bryant <russell@ovn.org>
Acked-by: Ben Pfaff <blp@ovn.org>