Only skip update if the set of available calendars did not changed

[duburcqa]

This is necessary to automatically update sources for which the calendars have been added or deleted by another client than roundcube. It is typically the case when managing sharing access in nextcloud while still being able to view them in roundcube.

[JodliDev]

Thanks a lot for this! :) Sorry for my late reaction. I will test in the next coming days and the accept the PR

[duburcqa]

any update on this ?

[JodliDev]

Apologies for my terrible response time!