python: Drop usage of long type.

python: Drop usage of long type.

Python 2 has both long and int types.  Python 3 only has int, which
behaves like long.

In the case of needing a set of integer types, we can use
six.integer_types which includes int and long for Python 2 and just int
for Python 3.

We can convert all cases of long(value) to int(value), because as of
Python 2.4, when the result of an operation would be too big for an int,
the type is automatically converted to a long.

There were several places in this patch doing type comparisons.  The
preferred way to do this is using the isinstance() or issubclass()
built-in functions, so I converted the similar checks nearby while I was
at it.

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