bootupctl: Clear failure status from previous runs

If for whatever reason a bootupd command fails, it will leave the
systemd service unit in a failed state and systemd will then refuse to
run a unit under the same name with `systemd-run` again until the
failure is cleared.

Thus systematically call `systemctl reset-failed` before calling
`systemd-run` to clear any potential failures from previous calls.

See: coreos#707

src/cli/bootupctl.rs

@@ -154,6 +154,11 @@ fn ensure_running_in_systemd() -> Result<()> {
     require_root_permission()?;
     let running_in_systemd = running_in_systemd();
     if !running_in_systemd {
+        // Clear any failure status that may have happened previously
+        let _r = Command::new("systemctl")
+            .arg("reset-failed")
+            .arg("bootupd.service")
+            .spawn()?.wait()?;
         let r = Command::new("systemd-run")
             .args(SYSTEMD_ARGS_BOOTUPD)
             .args(std::env::args())