Opencensus 0.28.0 bug with Distributed Tracing

Opencensus version 0.28.0 has an issue that might crash internal threads when there is clock skew in the running machine. This would cause threads to hang forever in a lock.

In the SpannerIO.readChangeStreams SDF, we are using opencensus to get distributed tracing. Due to the bug above, we could reach a condition where a close Span would never return, causing the job to get stuck.

This bug would only be present if the Connector was used alongside the faulty version of the opencensus-impl dependency (<= 0.28.0), as the Apache Beam project only depends on the opencensus-api.

Nevertheless, we would like to update the opencensus-api version to the newest one (0.31.0), in order to avoid customer confusion.