LU-6245 utils: split kernel comm between user and kernel

LU-6245 utils: split kernel comm between user and kernel

The kernel communication code used for HSM and changelog is
entangled. Move the user space bits into the liblustreapi. This will
also help for a possible relicensing. The kernel portion is also moved
from libcfs to obdclass.

The original libcfs_kernelcomm.h header is split into three parts:

  * lustre_kernelcomm.h, a new header for the kernel parts;
  * uapi_kernelcomm.h, a new header for the data structures shared
    between userspace and kernelspace;
  * lustreapi_internal.h receives the private liblustreapi prototypes.

The original code in kernel_user_comm.c is split into two parts:

  * obdclass/kernelcomm.c for the kernel part. filp_user_write() was
    moved there, and linux-fs.c deleted;
  * liblustreapi_kernelconn.c for the user part. The calls to CDEBUG
    have been removed, and calls to CERROR have been transformed to
    llapi_err_noerrno. The type lustre_kernelcomm has been removed and
    replace by struct lustre_kernelcomm.

Various names and filenames have been harmonized to *kernelcomm*.

The unused symbol KUC_FL_BLOCK has been removed.

Signed-off-by: frank zago <fzago@cray.com>
Change-Id: Id15ab6ea23a160e0aa0517a1a890266b2e971982
Reviewed-on: http://review.whamcloud.com/14270
Tested-by: Jenkins
Reviewed-by: Nathan Rutman <nathan.rutman@seagate.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-by: Dmitry Eremin <dmitry.eremin@intel.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>