LU-6245 libcfs: move uid handling to linux directory

LU-6245 libcfs: move uid handling to linux directory

Simple patch to move the uid handling added to handle
older kernels to the linux directory. The linux
directory is where we handle APIs of newer kernels
with older distribution kernels.

Test-Parameters: trivial

Change-Id: Ie3676d33ce33ebc0f98ffa460cba37ab55928617
Signed-off-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-on: http://review.whamcloud.com/22139
Tested-by: Jenkins
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Frank Zago <fzago@cray.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>