Ignore InvariantCultureNpgsqlCopySerializer test when running under protocol version 2

The test created by #92 hangs when running under protocol 2. It seems NpgsqlCopySerializer has a problem with this protocol version.
Ignored for while when running under protocol 2 until we verify why this is happening.
Merge pull request #103 from franciscojunior/ignore-copyserializer-test-from-pr92-protocol-2

Ignore InvariantCultureNpgsqlCopySerializer test when running under prot...