Bump packer build timeout to 90 minutes

With all of the consolidation of packaging into the new baseline
scripts as well as known slowness in Vexxhost builds for baseline
are now taking around 60 minutes to run. Bump to 90 minutes so that
there is a buffer for us to continue developing baseline.

Change-Id: I195a74d902111c937bebf7c8e599a3d641e74a37
Signed-off-by: Thanh Ha <thanh.ha@linuxfoundation.org>