Numerous errors in Netty instrumentation when using GRPC

[dhilpipre]

Description

The Netty instrumentation for Netty 4.1.16 includes reading inbound headers on Http2. When GRPC is being used, there are numerous errors being logged to the agent log at a high rate. If logging level is set to FINER or FINEST the logs were fill up very fast. These errors are caused by the fact that the GRPC Http2 header class expects an io.netty.util.AsciiString input and the agent is passing a String object.

In order to get rid of all the error log, it is necessary to put in a check for GRPC and if it is GRPC then create an AsciiString from the String and pass the AsciiString to GRPC.

I have coded this already and will generate a pull request referring back to this bug.

[workato-integration]

https://new-relic.atlassian.net/browse/NR-352057