Update autotest/install_then_upgrade

autotest/install_then_upgrade

@@ -95,7 +95,7 @@ fi
 
 apt-get -qq update
 
-apt install phpmyadmin
+apt-get -q -y install phpmyadmin
 
 echo ----------- Upgrading -----------
 diff /tmp/from_repo /tmp/local_versions | grep '^> ' | sed -e 's|> ||' | tr ' ' '\t'