Merge branch 'fix_regression_in_duplicity_remove-older-than' into 'master'

Actually run duplicity remove-older-than. Fix #11345

Closes #11345

See merge request liberate/backupninja!64

handlers/dup.in

@@ -313,7 +313,7 @@ fi
 if [ "$keep" != "yes" ]; then
    debug "executing duplicity remove-older-than"
    debug "$nice $execstr_precmd duplicity remove-older-than $keep --force $execstr_options $execstr_serverpart"
-   if [ ! $test ]; then
+   if [ $test = 0 ]; then
       export PASSPHRASE=$password
       export SIGN_PASSPHRASE=$signpassword
       export FTP_PASSWORD=$ftp_password