What the cache manager needs to know about rxosd

What the cache manager needs to know about rxosd

this patch contains only the RPC interface to rxosd which already
contains the definition of all RPCs not just those few used in the
cache manager.

The code which calls these RPCs will follow in subesquent patches.

Change-Id: Ia90934b06e809d0a34ed5d4a0d77eed78b74780c
Reviewed-on: http://gerrit.openafs.org/3192
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>