LU-6153 libcfs: rename cfs_snprintf() to scnprintf()

LU-6153 libcfs: rename cfs_snprintf() to scnprintf()

Rename cfs_snprintf() to scnprintf() to match the existing kernel
function. Similarly rename cfs_vsnprintf() to vscnprintf(). Remove the
unused functions cfs_[v]snprintf().

Signed-off-by: John L. Hammond <john.hammond@intel.com>
Change-Id: I361a28959dc8a20ab0e152eaed00fd4adf78cc34
Reviewed-on: http://review.whamcloud.com/13517
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Tested-by: Jenkins
Reviewed-by: Dmitry Eremin <dmitry.eremin@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: James Simmons <uja.ornl@gmail.com>