LU-9340 lov: Initialize component extents unconditionally

LU-9340 lov: Initialize component extents unconditionally

LOV should initialize extent of components even they are not
instantiated because lov_io_iter_init() relies on this to issue
write intent RPC.

Signed-off-by: Jinshan Xiong <jinshan.xiong@intel.com>
Change-Id: Iaa452e3a0f3186cfea77866b7a1fabbc9feeec53
Reviewed-on: https://review.whamcloud.com/27116
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: James Simmons <uja.ornl@yahoo.com>