LU-4008 mdt: Shrink default LOVEA reply buffers

LU-4008 mdt: Shrink default LOVEA reply buffers

Instead of allocating maximum possible LOVEA for intent requests,
allocate a sane default to fit up to 100 stripes, should the size
be bigger, the buffer reallocation code will kick in.

Additionally, since quite awhile ago we no longer send
unlink cookies or EA data to the clients from unlinks/renames,
so we no longer need to allocate reply buffer for them in
mdt_close() and other such places.
Also clean up unused fields related to these buffers in
md_attr structure.

Change-Id: I4c5bfb5f2d39653d5612c90967d5e1ac83d441e6
Signed-off-by: Oleg Drokin <oleg.drokin@intel.com>
Reviewed-on: http://review.whamcloud.com/9322
Tested-by: Jenkins
Reviewed-by: Matt Ezell <ezellma@ornl.gov>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: James Simmons <uja.ornl@gmail.com>
Reviewed-by: Mike Pershin <mike.pershin@intel.com>