Use save_and_reraise_exception when reraise exception
Use save_and_reraise_exception when reraise exception

This commit fixes neutron core and common codes.

Partial-Bug: #1279813
Change-Id: Id109924c7ff9b4f0d74c23665016a54bfd7dff77

openstack/neutron-vpnaas,openstack/neutron-vpnaas,citrix-openstack-build/neutron-vpnaas,dougwig/x-neutron-vpnaas