LU-15840 lov: return st_blocks=1 for HSM released files

LU-15840 lov: return st_blocks=1 for HSM released files

The MDT will return st_blocks=1 for a HSM released file.
In the call ->coo_attr_get in LOV layer, the client should also
return st_blocks=1 for a HSM released file.

Otherwise, the client may get 0 block count. It is very easy to
reproduce this problem via the following commands for a archived
file:
	# $LFS hsm_restore $file
	# $LFS hsm_release $file
	# $LFS hsm_release $file
After release a file twice, the reported block count via stat()
call will become 0.

Change-Id: Id1841147e40a7df0ca615e887f324cff8e613f11
Signed-off-by: Qian Yingjin <qian@ddn.com>