Webflux + Kotlin lossing span

[xsmrcek]

Describe the bug
Instrumentation using agent is lossing span.
Every client request have new/different trecaparent.

Steps to reproduce
Build application from attachment, build docker image with app and nevest javaagent.
Configuration I use:
ENV OTEL_TRACES_EXPORTER="none"
ENV OTEL_METRICS_EXPORTER="none"
ENV OTEL_PROPAGATORS="tracecontext,b3,baggage"
I am testing just propagation now. ( I wan to use application insights javaagent in future/ As far as I know it is build on top of opentelemetry javaagent, so first I need this one working)
What did you expect to see?
Trace headers (traceparent, traceid, spanin etc is generated/propagated correctly)
What did you see instead?
New trace headers for every request.
What version are you using?
newest opentelemetry-javaagent (1.10.0)

Environment
openjdk 15 2020-09-15
spring-boot-starter-parent 2.5.5 (webflux)
kotlin 1.5.31
logbook (for logging) 2.4.1

[xsmrcek]

I wan't able to upload an attachment, so I upload minimal exmaple here: https://github.com/xsmrcek/minimal-example