Fix nested child span support for Zipkin

[hekike]

0.14.0 unfortunately, breaks nested child support in Zipkin.

• fix support for nested child spans
• test for published spans

Related to:
https://github.com/census-instrumentation/opencensus-node/pull/545/files#diff-427d5fa67f108e0a06e484bd47da9015R81

[codecov-io]

Codecov Report

Merging #574 into master will increase coverage by 0.24%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #574      +/-   ##
==========================================
+ Coverage   95.08%   95.33%   +0.24%     
==========================================
  Files         150      150              
  Lines        9877    10704     +827     
  Branches      725      756      +31     
==========================================
+ Hits         9392    10205     +813     
- Misses        485      499      +14

Impacted Files	Coverage Δ
src/zpages-frontend/page-handlers/templates-dir.ts	80% <0%> (-20%)	⬇️
src/internal/cls.ts	91.66% <0%> (-8.34%)	⬇️
src/tags/propagation/text-format.ts	95.65% <0%> (-4.35%)	⬇️
src/zpages-frontend/latency-bucket-boundaries.ts	70.42% <0%> (-2.82%)	⬇️
src/tags/propagation/binary-serializer.ts	97.26% <0%> (-0.47%)	⬇️
src/internal/string-utils.ts	100% <0%> (ø)	⬆️
src/index.ts	100% <0%> (ø)	⬆️
test/test-tag-map.ts	100% <0%> (ø)	⬆️
test/test-no-record-span.ts	100% <0%> (ø)	⬆️
test/test-metric-producer-manager.ts	100% <0%> (ø)	⬆️
... and 34 more

---

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 405758f...b63c7b8. Read the comment docs.

[mayurkale22]

LGTM

[mayurkale22]

@hekike Let me know if you are waiting for this release?

[hekike]

@mayurkale22 thanks for asking, currently I just use 0.13.0, so it's not blocking.