python: Drop use of sys.maxint.

python: Drop use of sys.maxint.

sys.maxint does not exist in Python 3, as an int does not have a max
value anymore (except as limited by implementation details and system
resources).

sys.maxsize works as a reasonable substitute as it's the same as
sys.maxint.  The Python 3.0 release notes have this to say:

  The sys.maxint constant was removed, since there is no longer a limit
  to the value of integers. However, sys.maxsize can be used as an
  integer larger than any practical list or string index. It conforms to
  the implementation’s “natural” integer size and is typically the same
  as sys.maxint in previous releases on the same platform (assuming the
  same build options).

sys.maxsize is documented as:

  An integer giving the maximum value a variable of type Py_ssize_t can
  take. It’s usually 2**31 - 1 on a 32-bit platform and 2**63 - 1 on a
  64-bit platform.

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