rebuild recovery patch in sign_target_files_apks

The target_files zip should now contain the recovery-from-boot patch
and the script to install it.  This means that sign_target_files_apks,
which generates a signed target_files from an unsigned target_files,
now needs to recompute the patch and script (taking into account the
key replacement, property changes, etc., that it does) so its output
contains the correct patch.

Change-Id: I18afd73864ba5c480b7ec11de19d1f5e7763a8c0