[XFS] Fixing KDB's xrwtrc command, also added the current process id into

the trace.

SGI-PV: 948300
SGI-Modid: xfs-linux-melb:xfs-kern:208069a

Signed-off-by: Yingping Lu <yingping@sgi.com>
Signed-off-by: Nathan Scott <nathans@sgi.com>