adb: remove extraneous stat in sync_recv.

We do a remote stat to get the file's size before pulling in sync_recv,
but all of the callers to sync_recv have already done a stat. Pass the
expected file size into sync_recv to remove its stat.

Bug: http://b/31289465
Test: python test_device.py
Change-Id: I7ca8ed11c6134e5954acac86626f880ade3ec696