LU-9067 utils: ensure debugfs is mounted

LU-9067 utils: ensure debugfs is mounted

With the move of lustre to sysfs and tracepoint it
will become critical to have debugfs mounted. On
older platforms like RHEL6 its not mounted by default.
Also it is possible that debugfs could become umounted
by accident thus disabling needed functionality
to control lustre. Add to libcfs.a a function that
is always called to ensure debugfs is mounted.
If debugfs is not mounted then mount it if the caller
is root.

Change-Id: I21f85ba252b67bfbc22b23920e2ccaffc196074b
Signed-off-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-on: https://review.whamcloud.com/25182
Reviewed-by: Bob Glossman <bob.glossman@intel.com>
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>