Disable ramdisk builds and tests.

now that gce_ramdisk is pretty much gone, time has come to rip out
metadata and services that depend on it.
I was hoping to keep these around for a bit longer, but it simply
doesn't make sense.

Change-Id: I5f1792dafa34b2520af5c4bc45e798f51e39cb4e
(cherry picked from commit dd42361577d0943a1bf744eada29e3e64a4635d5)
8 files changed