releasetools: Explicitly pass the SHA-1 of source boot image to PatchCheck.

Although the SHA-1 of the source boot image has been encoded in the
filename, the updater code currently doesn't extract that and would fail
to find a matching backup from /cache. This could lead to corrupt
install, if it's interrupted while patching the boot image.

Bug: 80630342
Test: Generate an non-A/B incremental package. Verify the script.
Change-Id: Ie2b1a90836c3ccb4758e1a2d9b69a88de94ae0c7