run: Set hostname to `cosarun`
Let's provide a hostname by default, because the default
`ibm-p8-blah-blah-blah` is just too long.  This was a subtle
fallout from the `cmd-run` gutting.
set -euo pipefail
# This used to contain a lot of its own custom logic. All of the qemu code
# now lives inside mantle/kola.
-exec kola qemuexec --add-ignition=autologin -U --auto-cpus "$@"
+exec kola qemuexec --hostname cosarun --add-ignition=autologin -U --auto-cpus "$@"
