Similar to what is happening in Neutron, this commit renames and moves unit
test files so that they match the directory structure of the code tree.
Since the VPN repo's test files have imports from Neutron, there are import
changes as well, to the imports to match the Neutron test file organization.
A check script is added to monitor the test file naming and locations (to
ensure consistency).
Change-Id: I875285230127ed660137d271f7e98d82eb57ffab
Partial-Bug: #1440834
bc2a1d7754