Fix the attribute for scteken_clear() (change it back from the user
user default normal attribute to the current attribute).

This change only fixes a logic error. scterm_clear() used to be
used for terminal reset, but teken uses a general fill function for
that, leaving scterm_clear() only used for initialization and mode
change, when using the user default attribute is correct. It is not
really a terminal function, but needs to sync its changes with the
terminal layer. Syncing of the attribute is currently broken for
terminal reset, but works for initialization and mode change.