UpgradeHandler may not notify the application of the initial data.

[pmd1nh]

Describe the bug
Client can send an Upgrade request along with some data immediately after the upgrade request headers (before receiving 101 Switching Protocols response). If the initial package (headers + data) comes into the server faster than the channel can parse/handle, those data are read and hold in the channel's buffer but does not notify the application (via registered ReadListener) for handling; thus appear to be missing.

It can happen after a server cold start. Subsequent requests should be fine.

If the initial data is sent AFTER the client received the initial response of 101 Switching Protocols , it always work. i.e

request >> upgrade request
response << `101 Switching Protocols`
request >> data

Though this is not a requirement (yet), it is recommended to send data after received 101 response as the server may fail to upgrade and switch to new protocols; thus, the data ends up being discarded.

There is no server error or message

Steps to Reproduce
-Start server
-Send Upgrade request and some data immediately after the upgrade request headers.
-Application may not be notified of these initial data. (Typically happens in the first request after a server startup; all subsequent requests are fine).

Expected behavior
Application should always be notified of the available data.

Diagnostic information:

• OpenLiberty Version: [All]
• Affected feature(s) [servlet-3.1 or above]
• Java Version: [JDK 8 or above]

Additional context