Add post-install verification for BBOTAs

Similar to the assertations in file-based OTA, we perform verification
for block-based OTAs (BBOTAs) after updating a partition, for both of
the incremental and full OTAs. It increases the update time (~20s on
Nexus 6), but will capture unnoticed errors right away.

Bug: 21500869
Change-Id: I89ac8fe623b855721b7affd07cf9426a23433ab0

tools/releasetools/ota_from_target_files.py

@@ -917,6 +917,7 @@ else
 
   system_diff.WriteScript(script, output_zip,
                           progress=0.8 if vendor_diff else 0.9)
+
   if vendor_diff:
     vendor_diff.WriteScript(script, output_zip, progress=0.1)