Glide update and comment out usage of grpc-opentracing until fixed

[bufdev]

Here's the situation:

• grpc/grpc-go pushed a breaking change to their metadata API when they released 1.3.0
• If you call metadata.NewContext twice, the second call overrides the first, and metadata is lost Metadata context changes are not backwards compatible/break existing code grpc/grpc-go#1219
• grpc-ecosystem/grpc-opentracing did not have a corresponding release to handle this, causing yarpc/transport/x/grpc to break when we glide update (headers are no longer sent from client to server)

I commented out usages of grpc-opentracing for now until grpc-ecosystem/grpc-opentracing#29 is merged, and changed grpc-go in glide to be pinned to minor versions.

grpc-opentracing doesn't actually have releases either, so this makes it more problematic. We may want to review using it altogether.

[mention-bot]

@peter-edge, thanks for your PR! By analyzing the history of the files in this pull request, we identified @abhinav to be a potential reviewer.

[codecov]

Codecov Report

Merging #996 into dev will decrease coverage by 0.17%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##              dev     #996      +/-   ##
==========================================
- Coverage   80.66%   80.48%   -0.18%     
==========================================
  Files         194      194              
  Lines        9160     9158       -2     
==========================================
- Hits         7389     7371      -18     
- Misses       1411     1427      +16     
  Partials      360      360

Flag	Coverage Δ
#experimental	70.68% <ø> (-0.91%)	⬇️
#main	82.94% <ø> (ø)	⬆️

Impacted Files	Coverage Δ
transport/x/grpc/outbound.go	76.82% <ø> (-0.28%)	⬇️
transport/x/grpc/inbound.go	83.09% <ø> (-0.24%)	⬇️
transport/x/grpc/options.go	25% <0%> (-25%)	⬇️
transport/x/grpc/handler.go	53.03% <0%> (-15.16%)	⬇️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update e4dc746...e502586. Read the comment docs.

[HelloGrayson]

Sure - let's not block on opentracing integration while we're figuring out the core support story.