LU-6441 ptlrpc: fix sanity 224c for different RPC sizes

LU-6441 ptlrpc: fix sanity 224c for different RPC sizes

- fail_loc should be set on the OST side;
- an RPC can have 16 bulk descriptors at most, make the test case
  usable even with smaller RPC size.

Patch http://review.whamcloud.com/14399 added sanity.sh test_224c
to verify correct handling of failures with bulk transfers over 1MB,
but did not correctly handle the different transfer sizes possible.

Test-Parameters: trivial
Signed-off-by: Jinshan Xiong <jinshan.xiong@intel.com>
Change-Id: I9d0bc0c523cb71d95c6165066e666878c2a380cc
Reviewed-on: http://review.whamcloud.com/22403
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Niu Yawei <yawei.niu@intel.com>
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>