Implement required _handle_driver_error() for the LBaaSv2 driver
Implement required _handle_driver_error() for the LBaaSv2 driver

Issues:
Fixes #864

Problem:
Whenever an exception is thrown by neutron-lbaas for a driver operation
error the _handle_driver_error method is called on the provider driver.
We don't implement this and it causes another exception

Analysis:
Add function definition to the driver.  It does not perform any special
handling of the error.

Tests:
neutron_lbaas/test/tempest

jputrino/f5-openstack-lbaasv2-driver,richbrowne/f5-openstack-lbaasv2-driver,jlongstaf/f5-openstack-lbaasv2-driver,F5Networks/f5-openstack-lbaasv2-driver,jputrino/f5-openstack-lbaasv2-driver,F5Networks/f5-openstack-lbaasv2-driver,richbrowne/f5-openstack-lbaasv2-driver,jlongstaf/f5-openstack-lbaasv2-driver