releasetools: Fix error text in ota_from_target_files

property isn't the variable name, prop is

Change-Id: I0fc6adddfd51ba9bc79f6559c61cd831203c9e3d
Merge remote-tracking branch 'pac/pac-4.4' into pac-4.4
Make sure that OTA packages use MINIGZIP variable

Change-Id: I898f5e7d3e0afc1061c3f4ee66100ccbf1167ccc
Pass ota_custom_minigzip for Jenkins

Change-Id: Ia57cdf5097c13d6a7cb55ab9f22aa3e2b16d1d81