Deflake TestTSHSSH (#12401)
Deflake TestTSHSSH (#12401)

When shutting down, wait for the Teleport process to terminate, this
ensures that Go doesn't try to delete the TempDir while we're still
writing to it.
gravitational/teleport,gravitational/teleport,gravitational/teleport,gravitational/teleport,gravitational/teleport,gravitational/teleport