Windows: Do not pass relative paths to redirector

RDR_SetInitParams provides two paths to the redirector, the AFSCache
file path and the path of the %TEMP% environment variable.  If either
of these paths are relative paths and not absolute (or full) paths,
the redirector and the service will interpret them differently.
Ensure that the full paths are delivered to the redirector.

Change-Id: I48d9cd09d9292cc0e97c41da430026c20e097de1
Reviewed-on: http://gerrit.openafs.org/9074
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>