LU-3462 build: Repair "make dist"

LU-3462 build: Repair "make dist"

The "make dist" target should assemble a canonical tarball of the
lustre source tree.  Generally speaking, it should not be effected
by command line options given to the configure script.

For instance, all source files should appear in the tarball regardless
of whether or "--disable-server" is engadged.  Some recent LU-1330
landings have broken this by making compilation of some source files
optional, but failing to add those optional source files to EXTRA_DIST.

Change-Id: I20dc0f791a2a70f921d78c62b00992aa90aa0eaf
Signed-off-by: Christopher J. Morrone <morrone2@llnl.gov>
Reviewed-on: http://review.whamcloud.com/7054
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Liu Xuezhao <xuezhao.liu@emc.com>
Reviewed-by: Minh Diep <minh.diep@intel.com>
Reviewed-by: Brian J. Murrell <brian.murrell@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>