[PATCH] Fix the sunrpc cache/reader management properly.

[PATCH] Fix the sunrpc cache/reader management properly.

A recent patch changed the rpc/*/channel files to behave
differently depending on whether they were open for read or not.

This hadn't been tested thoroughly.  The cache_reader structure
that was now only allocated when opening for read, had a field that
was iused when writing.

This patch removes that field and takes a different approach to solving
the issue it addressed.

And it has been tested a bit better.