release: Stop publishing non-FS-tagged VM images

VM, BASIC-CI, and BASIC-CLOUDWARE images are published with the
filesystem type (UFS or ZFS) in the file name. For backwards
compatibility we have published the UFS images with no filesystem
in the filename (aka with the same file names as we used before we
supported building ZFS VM images); those are going away now.

This will not be MFCed.