Add test_valid_api_version in the test_constraints
Add test_valid_api_version in the test_constraints

There is a valid_api_version function in the constraints,but it has no
tests in the test_constraints. Therefore, I add test_valid_api_version.

Change-Id: Ic8dbe9c00f762513ec9a4ffc0b77e4e5d3e5d47b

smerritt/swift,psachin/swift,nadeemsyed/swift,hurricanerix/swift,tipabu/swift,nadeemsyed/swift,matthewoliver/swift,redbo/swift,nadeemsyed/swift,clayg/swift,smerritt/swift,clayg/swift,swiftstack/swift,prashanthpai/swift,notmyname/swift,smerritt/swift,openstack/swift,tipabu/swift,hurricanerix/swift,matthewoliver/swift,notmyname/swift,notmyname/swift,openstack/swift,swiftstack/swift,matthewoliver/swift,matthewoliver/swift,smerritt/swift,openstack/swift,hurricanerix/swift,psachin/swift,hurricanerix/swift,swiftstack/swift,psachin/swift,redbo/swift,notmyname/swift,prashanthpai/swift,nadeemsyed/swift,tipabu/swift,clayg/swift,psachin/swift,openstack/swift,tipabu/swift,clayg/swift