zip_archive: reject files that don't start with an LFH signature. am: dbacd826a1 am: 368ec42fa8 am: 6dbd1db1cf am: 58c10b2ab9  -s ours
am: 2dbba44e2d

Change-Id: I05eda8a0b1f41b979e5673b822865315244fc4ac