CC-2722: Overwrite errors on upgrade from 1.8.2 to 1.9.2-RC1

- fixed
- wasn't able to reproduce the first error msg

install_minimal/upgrades/airtime-1.9.0/airtime-upgrade.php

@@ -66,6 +66,7 @@ class AirtimeInstall{
         exec("rm -f /usr/bin/airtime-import");
         exec("rm -f /usr/bin/airtime-update-db-settings");
         exec("rm -f /usr/bin/airtime-check-system");
+        exec("rm -f /usr/bin/airtime-user");
     }
 
     public static function DbTableExists($p_name)