LU-506 kernel: FC15 - fix GCC 'set-but-unused' warnings

LU-506 kernel: FC15 - fix GCC 'set-but-unused' warnings

Eliminate a number of unused variables in the code that
caused GCC-4.6.0 to warn about "set-but-unused variables".
In some cases the variables are only used in
conditionally-compiled code, so they are used in some way
just to quiet the compiler.

Signed-off-by: Yang Sheng <ys@whamcloud.com>
Change-Id: I8b9b744c787fff4057722420866adea86d8240f5
Reviewed-on: http://review.whamcloud.com/1330
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Niu Yawei <niu@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>