LU-2800 autoconf: remove LC_FS_STRUCT_USE_PATH

LU-2800 autoconf: remove LC_FS_STRUCT_USE_PATH

struct fs_struct has been using struct path for working dirs
since v2.6.26.

We can remove the test and the dead code.

Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: James Simmons <uja.ornl@gmail.com>
Change-Id: I647eff05fa927e6d8b9865009a3e920c7971b7c5
Reviewed-on: http://review.whamcloud.com/5359
Tested-by: Hudson
Reviewed-by: Bob Glossman <bob.glossman@intel.com>
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>