Rethink buffer preselection

Rethink buffer preselection

As automatic buffer selection on startup clears the activity,
this will hopefully be the best solution without another clientsetting..

All versions will select the statusbuffer of a connecting network if
no valid buffer is currently selected.

Monolithic version will always start with the last selected buffer.
There is just no activity until next start.

Client will now only preselect the last buffer if the connection was not
closed by the user.
If the connection was closed manually or after fresh client start,
the statusbuffer of some connected network will be shown.