Investigate whether there is fallout from #60

[Raphael 'kena' Poss]

@tooolbox pointed out helpfully that #60 may have changed the protobuf package paths and thus the encoding of errors over the network.

This needs to be checked in a test. If there is any discrepancy, that needs to be dealt with a proper RegisterTypeMigration call.

[Raphael 'kena' Poss]

I have investigated this by looking at the binary protobuf encoding of test errors.

The protobuf package path is unchanged and remains cockroachdb.errorspb. There is no change in the binary encoding. So #60 does not require any change in apps.

Thanks @tooolbox for asking nevertheless.

[Matt Mc]

No problem, thanks for checking it out!