mkrootfs: Install OpenSSL 1.1

`mqttdpms` is linked against OpenSSL 1.1.  Rather than build multiple
copies that link to different versions, it's easier (for now) to just
install the old version of OpenSSL here.

mkrootfs.sh

@@ -28,6 +28,7 @@ dnf --installroot "${destdir}" install -y \
     nbd \
     openbox \
     openssh-server \
+    openssl1.1 \
     rsyslog \
     systemd \
     xinit \