LU-4746 libcfs: Use Linux kernel current_umask() function

LU-4746 libcfs: Use Linux kernel current_umask() function

Lustre not using kernel current_umask() function breaks GRSecurity
umask handling. This is also needed for the linux api cleanup.

Replaces current->fs->umask with more secure current_umask() function

Change-Id: Ide0b83eb3e6c69e1e2178ede37ce708227f1c107
Signed-off-by: Andrew Prout <ajprout@hotmail.com>
Signed-off-by: Cliff White <cliffwhi@intel.com>
Signed-off-by: James Simmons <uja.ornl@gmail.com>
Reviewed-on: http://review.whamcloud.com/11642
Tested-by: Jenkins
Reviewed-by: Bob Glossman <bob.glossman@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Dmitry Eremin <dmitry.eremin@intel.com>