Use Jan 1 2009 as timestamp in APKs and OTA update ZIPs.

Previously, the timestamp was one hour ahead of NotBefore of the
signer's certificate, adjusted for the current timezone. With this
change the MS-DOS timestamp in output APK/ZIP files is
Jan 1 2009 00:00:00.

Bug: 26864066
Change-Id: Id6263c38ac7042489ab695454f8e0fb2d85a3958