fix: unlock keyring in xstartup

[saw-jan]

GUI tests can fail due to unreliable unlocking of keyring: https://github.com/owncloud/client/issues/11619

So, unlock of keyring is now done in a xstartup file. This seems pretty reliable.

Tested builds:

• https://drone.owncloud.com/owncloud/client/18969
• https://drone.owncloud.com/owncloud/client/18970
• https://drone.owncloud.com/owncloud/client/18971
• https://drone.owncloud.com/owncloud/client/18972