rx: Make lock-free call data explicit

rx: Make lock-free call data explicit

For speed, the application thread accesses a number of elements of
the call structure without holding the call lock. This is safe, as
long as the application thread is the only place in which these
items of data are accessed.

Make this distinction explicit by creating a new structure to hold
all of these fields, and include this structure within the rx_call.

This turns up one place in the code (SendXmitList) which accesses an
application private piece of data in the listener and event threads.
A forthcoming patch will fix this.

Change-Id: I7b5ffb8b5ce68a2186e37ae64461fe356a40603e
Reviewed-on: http://gerrit.openafs.org/8285
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>