Remove duplicated tests for check_ovs_vxlan_version

test_ovs_lib, test_ovs_neutron_agent and test_ofa_neutron_agent
have duplicated same unit tests for check_ovs_vxlan_version.
This commits removes tests from ovs/ofa_neutron_agent.

Change-Id: Ia028a4afc1c8154f895187c979d23b626ab4ae3a
Closes-Bug: #1301337
Merge "Remove duplicated tests for check_ovs_vxlan_version"