Not set parentId in case parentId is empty

[andriy-fedechko-imprivata]

Fixes # (issue)
The root Span is not displayed in SignalFX (Splunk APM) when data is exported via Zipkin exporter.
According to https://zipkin.io/zipkin-api/#/ (ListOfSpans seection) the parentId element should be absent for root span

Changes

added logic into Zipkin's recordable implementation to add parentId element only when parentId is valid.

[linux-foundation-easycla]

The committers are authorized under a signed CLA.

• ✅ Andriy Fedechko (6c810d6)

[lalitb]

thanks for the fix. You would have to authorize easyCLA before it can be merged.

Also to format code before commit, run below from root directory:
$ ./ci/do_ci.sh format

[codecov]

Codecov Report

Merging #943 (2638700) into main (f4ff74c) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #943   +/-   ##
=======================================
  Coverage   95.36%   95.36%           
=======================================
  Files         160      160           
  Lines        6780     6780           
=======================================
  Hits         6465     6465           
  Misses        315      315