Log the session exception when ownCloud is not installed
Handle ownCloud logging when data dir not created
Include exception message in log entry when session fails to start
Merge branch 'master' of github.com:owncloud/core into fix-unlogged-session-error
Merge pull request #5303 from owncloud/fix-unlogged-session-error

Log an error when session initialization fails before ownCloud is intalled