Remove ssync iter_hook usage

Apparently that disappeared and now the whole thing does on its own what this
was trying to achieve.

Change-Id: If20016cb80c855e3e8373de5d56926ef8f8e7dac
use diskfile in ssync_sender tests

Change-Id: I7993de98ce3eb4839fa5d72d1b6ce08e4a7c1451
Merge "Remove ssync iter_hook usage"
Merge "use diskfile in ssync_sender tests"