LU-8680 osc: soft lock - osc_makes_rpc()

LU-8680 osc: soft lock - osc_makes_rpc()

It is possible that an osc_extent contains more than 256 chunks, and
the IO engine won't add this extent in one RPC
(try_to_add_extent_for_io) so that osc_check_rpcs() run into a loop
upon this extent and never break.

This patch changes osc_max_write_chunks() to make sure the value
can cover all possible osc_extent, so that all osc_extent will be
added into one RPC.

This patch also add another field erd_max_extents in extent_rpc_data
to make sure not to add too many fragments in a single RPC.

Signed-off-by: Bobi Jam <bobijam.xu@intel.com>
Change-Id: Icf58a6bd04655bb9aa5589dd002e118c21ed932d
Reviewed-on: http://review.whamcloud.com/23326
Reviewed-by: Jinshan Xiong <jinshan.xiong@intel.com>
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Niu Yawei <yawei.niu@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>