Results 2 issues of Zioyi

## What does this pull request do? I add code for supporting Grpc Client call ## Related issues closes #ISSUE [645](https://github.com/elastic/apm-agent-python/issues/645)

agent-python
community
stretch

In my environment of Window8.1, browsermob-proxy-py will be dead after running a time. Is there others met this codition?