Move dhparam creation

Now that all cloudrons have the dhparams file, we can generate this
*after* restoring from backup and if required.

setup/start.sh

@@ -199,10 +199,6 @@ if ! grep "^Restart=" /etc/systemd/system/multi-user.target.wants/nginx.service;
     echo -e "\n[Service]\nRestart=always\n" >> /etc/systemd/system/multi-user.target.wants/nginx.service
     systemctl daemon-reload
 fi
-# This is here, since the splash screen needs this file to be present :-(
-if [[ ! -f "${BOX_DATA_DIR}/dhparams.pem" ]]; then
-    openssl dhparam -out "${BOX_DATA_DIR}/dhparams.pem" 2048
-fi
 systemctl start nginx
 
 # bookkeep the version as part of data
@@ -320,6 +316,11 @@ if [[ ! -z "${arg_tls_config}" ]]; then
         -e "REPLACE INTO settings (name, value) VALUES (\"tls_config\", '$arg_tls_config')" box
 fi
 
+echo "==> Generating dhparams (takes forever)"
+if [[ ! -f "${BOX_DATA_DIR}/dhparams.pem" ]]; then
+    openssl dhparam -out "${BOX_DATA_DIR}/dhparams.pem" 2048
+fi
+
 set_progress "60" "Starting Cloudron"
 systemctl start cloudron.target