LU-1364 utils: add lfs 'poollist' subcommand

LU-1364 utils: add lfs 'poollist' subcommand

Instead of adding a new subcommand this updates
the lfs man page.  pool_list is the preferred usage,
we just make all the docs match.

Signed-off-by: Bob Glossman <bogl@whamcloud.com>
Change-Id: I3f0a6692923e4ff8359afc8a3558ee404ffc4365
Reviewed-on: http://review.whamcloud.com/2734
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: Hudson
Reviewed-by: Richard Henwood <rhenwood@whamcloud.com>
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>