LU-506 kernel: FC15 - small changes

LU-506 kernel: FC15 - small changes

   -- stacktrace_ops.{warning(), warning_symbol()} removed.
   -- sk_sleep() helper added.
   -- quota_on() 4 parameter change to use 'struct path'.
   -- fs_struct.lock change to use spin_lock.
   -- other trivial changes.

Change-Id: Ic9bf47454b19c1cfc3e41cd3aebbabb074f6110f
Signed-off-by: Yang Sheng <ys@whamcloud.com>
Reviewed-on: http://review.whamcloud.com/1864
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Lai Siyao <laisiyao@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>