Move vmm_vhost out of external/rust/crates

That directory is for projects taken from crates.io, but vmm_vhost
actually tracks the fork in chromium which is the one that works with
crosvm.

Bug: 187839847
Change-Id: I66d696e9a3d2e641b0277e2b1a6a5fa0ac39fab3
1 file changed