Clear sensitive content when logging out fixes #1060

Clear sensitive content when logging out fixes #1060

The current position inside the Workspace is saved via the StateProvider
separately thus this clearing operation do not lose the previous selection.

As a side effect by calling setContent(null) on logout we also fix the
following bug:

when logging out while the Syslog tab of the Node panel was displayed,
you had to login twice due a to a race condition in the store
load of the Syslog panel. ( The login call could complete successfully
before a backgroup store load, causing the faild store load call
to redisplay a login window)