[BUG] URL of old servers (not supported) shows an non-accurate error message

[jesmrec]

Server versions older than 9.1 are not supported since the Android app has moved to the new webDAV endpoints. For this reason, it is not posible to login in these older versions anymore.

If you try to login, the error is:

Local copy not be renamed; try a different name

Error message should show the correct situation, f. ex. :

Server version not supported anymore, please move to a newer one

or similar one.

Login feature in new architecture (#2608) is a good candidate for doing that change

[jesmrec]

In scope of #2636

[jesmrec]

This is already done. It will be available in 2.15 as part of the end of support of older than 10 servers.