Add or remove dynamic dns have no effect if there is no provider

src/freedombone-utils-dns

     if [[ $ONION_ONLY != "no" ]]; then
         return
     fi
+    if [[ "$DDNS_PROVIDER" == 'none' ]]; then
+        return
+    fi
     if [ ! -f /etc/inadyn.conf ]; then
         echo $'Unable to find inadyn configuration file /etc/inadyn.conf'
         exit 5745
     if [[ $ONION_ONLY != "no" ]]; then
         return
     fi
+    if [[ "$DDNS_PROVIDER" == 'none' ]]; then
+        return
+    fi
     if [ ! -f /etc/inadyn.conf ]; then
         echo $'Unable to find inadyn configuration file /etc/inadyn.conf'
         exit 5745