Use code generated by protobuf go compiler 1.2

The protobuf for this branch was compiled with a newer version, v1.2. This had some changes on the the struct fields. A few got added, which broke tests that performed deep equal tests. For example an XXX_sizecache field was added to the messages, which sometimes is set but is not set when settting up a test.

By depending on equals the XXX_sizecache fields were compared, where the response would set them. By using proto.Equal() as suggested: https://groups.google.com/d/msg/protobuf/N-elvFu4dFM/6fGxs1v1AgAJ this problem is fixed.

Struct literal assignments were updated so tests would run again too.

Related to: gitaly-proto!266 (merged)