install: Include no-dist-upgrade in args list.

This was missed out in 2e51ac8c49

scripts/lib/install

@@ -12,6 +12,7 @@ Other options:
   --self-signed-cert
   --no-init-db
   --cacert
+  --no-dist-upgrade
 
 The --hostname and --email options are required,
 unless --no-init-db is set and --certbot is not.
@@ -21,7 +22,7 @@ EOF
 
 # Shell option parsing.  Over time, we'll want to move some of the
 # environment variables below into this self-documenting system.
-args="$(getopt -o '' --long help,no-init-db,self-signed-cert,certbot,hostname:,email:,cacert: -n "$0" -- "$@")"
+args="$(getopt -o '' --long help,no-init-db,no-dist-upgrade,self-signed-cert,certbot,hostname:,email:,cacert: -n "$0" -- "$@")"
 eval "set -- $args"
 while true; do
     case "$1" in