Fix one more grpc wrong direction bug

[grcevski]

This PR fixes two more edge case with processing gRPC requests in eBPF:

1. The gRPC response can be split. The responding service can send one response back and then follow-up with a close frame. In some rare instances we can interpret the second response as a new gRPC start. I added a check that a start cannot be an end at the same time.
2. In a previous PR I detected that gRPC requests can be split, but when I detected the wrong situation I didn't clean-up the wrong grpc info, so subsequent request may continue from it. This PR adds the delete.

I also fixed the issue reported in #920.

Closes #920

[grcevski]

Thanks @marctc !