nfsstat: Add --list flag

nfsstat.c: Adds the --list flag to print information in a list format
   instead of the standard multi-column format
nfsstat.man: Updates the manpage to include the --list flag.

Signed-off-by: Kevin Constantine <kevin.constantine@disneyanimation.com>
Signed-off-by: Steve Dickson <steved@redhat.com>