LU-9008 pfl: Read should not trigger layout write intent

LU-9008 pfl: Read should not trigger layout write intent

In lov_io_rw_iter_init(), only write not read operation should
trigger layout write intent.

For append write, it has to make sure all uninited components
are instantiated.

Page mkwrite should also trigger write intent.

Fixed sanity-pfl test cases as well - in order to instantiate
a component by truncate, the truncated size must be within the
extent of component.

Signed-off-by: Jinshan Xiong <jinshan.xiong@intel.com>
Signed-off-by: Bobi Jam <bobijam.xu@intel.com>
Change-Id: I3c5257c5799ae0df35a572b9ee981f583260e8ec
Reviewed-on: https://review.whamcloud.com/26499
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>