Don't use volatile when it makes no sense

Don't use volatile when it makes no sense

The demand attach code defines volume pointers as volatile in
a number of places, despite the fact that the values in question
aren't being shared between multiple threads. It then also passes
these volatile pointers into functions which don't treat them as
volatile (and even to some which assign them to registers).

This patch simply removes the use of volatile in this situation.

Reviewed-on: http://gerrit.openafs.org/550
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>