When ReadFromBuffer returns ResumeFromDiskError, the function now:
- Attempts to read from disk if ReadFromDiskFn is available
- Checks if the client is still connected via waitForDataFn
- Waits for notification or short timeout before retrying
- Continues the loop instead of immediately returning the error
This fixes TestNewLogBufferFirstBuffer which was failing because the
function returned too early before data was available in the buffer.
221b352593