Update grpc-opentracing to latest version at new home

[bboreham]

This is primarily to stop marking cancelled operations as errors - opentracing-contrib/go-grpc#1

Also update weaveworks/common to make all use of grpc-ecosystem libraries consistent, and bring in one bug fix "Fix dropped namespace in url parsing (weaveworks/common#128)".

[tomwilkie]

Are we sure https://github.com/opentracing-contrib/go-grpc is the new home for https://github.com/grpc-ecosystem/grpc-opentracing/tree/master/go/otgrpc? Is there any 'official' decision here?

[bboreham]

Issues went ignored in the latter; I found mention of the move somewhere and my PR was merged in the former.

[tomwilkie]

I've sent an email to both communities so see what the latest on this is.

[thisisnotapril]

From the gRPC perspective; we're happy to point folks wherever. I'd like to confirm the correct repo with the project maintainers though, and I'm not clear on who that is?

[Falco20019]

There already is an unmerged PR at grpc-ecosystem/grpc-opentracing#43
All our OpenTracing contribution projects can be found at https://github.com/opentracing-contrib following the structure <language>-<framework>. So please use https://github.com/opentracing-contrib/go-grpc as official repository. This was officially decided here: opentracing-contrib/meta#39

[tomwilkie]

Thanks @Falco20019, that LGTM.