[UT] Reduce the port binding retries to 1 in ``TestPortsV2``
[UT] Reduce the port binding retries to 1 in ``TestPortsV2``

In ``TestPortsV2`` tests, set the
``neutron.plugins.ml2.plugin.MAX_BIND_TRIES`` to 1 to minimize the
number of retries during a failed port binding. That shortens all
test cases execution time if a port binding is executed.

Trivial-Fix

Change-Id: If0473031797984aab5b36c479fcb774e57ff5624

openstack/neutron,mahak/neutron,openstack/neutron,openstack/neutron,mahak/neutron,mahak/neutron