pass blobs to applypatch in incremental OTAs

applypatch now takes patches as blob-valued arguments instead of just
filenames, eliminating the need to unpack all patches to /tmp before
starting to apply them.

Revert the last change I made where sha1_check(read_file(...)) was
substituted for apply_patch_check(...).  apply_patch_check() knows to
check /cache/saved.file if the original source file is missing or has
a bad checksum, which is important if the device loses power or
otherwise restarts during patching.

Change-Id: Ia5b761474b0f809a5a5eed29455b1b145145699e
diff --git a/tools/releasetools/amend_generator.py b/tools/releasetools/amend_generator.py
index f3dceca..b543bf7 100644
--- a/tools/releasetools/amend_generator.py
+++ b/tools/releasetools/amend_generator.py
@@ -100,6 +100,10 @@
     self.script.append("".join(out))
     self.included_files.add(("applypatch_static", "applypatch"))
 
+  # Not quite right since we don't need to check /cache/saved.file on
+  # failure, but shouldn't hurt.
+  FileCheck = PatchCheck
+
   def CacheFreeSpaceCheck(self, amount):
     """Check that there's at least 'amount' space that can be made
     available on /cache."""