[issue4845] Kolab calendar resource removed for some users (RT#10122)

This was reported by serveral users. When they start Kontact their Kolab
Calendar is removed. This is a regression exposed by the new code that only
allows a single calendar resource.

A first analysis on the debug output shows that in the case where the Kolab
resource gets deleted:
libkcal: CalendarResources::init( calendar ) is called twice.

The Second time this then leads to:
kresources: Factory::resource( imap, config )
kontact: KolabFactory: Not loading more kolab resources

The second kolab resource is not loaded but the first is not shown in the GUI.
If you try to add a new resource with the GUI it fails. If you close Kontact the
resource configuration of the "invisible resource" is not saved and on the next
start it is gone.

For some users this happens very reliable, mostly right after session login. For
me it happened once in dozends (maybe hundreds) of starts on my test machine.

Attached is the full log of the startup where the calendar was removed.
File 'calendar_removed.log' not attached - you can download it from https://roundup.kolab.org/file1723.

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assignedto: allen
files: calendar_removed.log
keyword: enterprise35, kde client, kkc
messages: 28714
nosy: aheinecke, allen, emanuel, laurent, ludwig, sergio, till, vkrause
priority: urgent
status: unread
title: Kolab calendar resource removed for some users (RT#10122)

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Kolab issue tracker <[email protected]>
<https://roundup.kolab.org/issue4845>
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