Fix some grammatical errors in TESTING.rst
Fix some grammatical errors in TESTING.rst

TrivialFix.

Change-Id: I1a0c2b2da9d6ae0a52028420a98f5ae17e8d6855

mahak/neutron,noironetworks/neutron,openstack/neutron,mahak/neutron,eayunstack/neutron,openstack/neutron,huntxu/neutron,mahak/neutron,noironetworks/neutron,openstack/neutron,huntxu/neutron,eayunstack/neutron