prow: Test most recent FreeBSD-12-0 images (#536)
prow: Test most recent FreeBSD-12-0 images (#536)

FreeBSD 12.0 is on its release cycle and their alpha releases are being
released under freebsd-12-0 image-family and the freebsd-12-0-snap is
deprecated until the release comes up.
GoogleCloudPlatform/compute-daisy,adjackura/compute-image-tools,GoogleCloudPlatform/compute-image-tools,zmarano/compute-image-tools,GoogleCloudPlatform/compute-daisy,adjackura/compute-image-tools,GoogleCloudPlatform/compute-image-import,zmarano/compute-image-tools,GoogleCloudPlatform/compute-image-import,GoogleCloudPlatform/compute-image-tools,GoogleCloudPlatform/compute-image-tools,GoogleCloudPlatform/compute-image-import,adjackura/compute-image-tools,zmarano/compute-image-tools