LU-8460 osc: max_pages_per_rpc should be chunk size aligned

LU-8460 osc: max_pages_per_rpc should be chunk size aligned

max_pages_per_rpc should be chunk size aligned.

obd_brw_size need to be at least one block size.

Improve the LASSERT() to an LASSERTF() that prints the related
parameters to help debug problem.

Signed-off-by: Bobi Jam <bobijam.xu@intel.com>
Change-Id: If73b8f05052f96970f3e97015a4642152ace2a38
Reviewed-on: http://review.whamcloud.com/21825
Tested-by: Jenkins
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Jinshan Xiong <jinshan.xiong@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>