Print SHA-1 in hex for corrupted blocks

It will be helpful for debug if we know which blocks are corrupted after
a verification failure. This CL prints the SHA-1 for each source block
in a transfer command if these blocks don't have an expected hash. And
along with the correct SHA-1, we will catch the corrupted blocks.

Bug: 21124445
Test: Printed the mismatched SHA-1 for bullhead during an update.
Change-Id: I683d4bdaf9a335035045b3f532b3a265b2fcbbfc