Fix incorrect error message occurence when re-adding the trust

You cannot re-add the trust and modify the range in the process.
The check in the code was malfunctioning since it assumed that
range_size parameter has default value. However, default value
is assigned only later in the add_range function.

https://fedorahosted.org/freeipa/ticket/3870
Fix nsSaslMapping object class before configuring SASL mappings.

This is a workaround for <https://fedorahosted.org/389/ticket/47490>.

https://fedorahosted.org/freeipa/ticket/3778