Add 'memory' console.logging

If console.logging is not desired, but reconstituting the screen is,
provide 'memory' as a method to do that.

On slow disks this can significantly improve performance.

confluent_server/confluent/config/attributes.py

@@ -336,7 +336,7 @@ node = {
         'description': ('Indicate logging level to apply to console.  Valid '
                         'values are currently "full", "interactive", and '
                         '"none". Defaults to "full".'),
-        'validvalues': ('full', 'interactive', 'none'),
+        'validvalues': ('full', 'memory', 'interactive', 'none'),
     },
     'console.method': {
         'description': ('Indicate the method used to access the console of '

confluent_server/confluent/consoleserver.py

@@ -234,7 +234,7 @@ class ConsoleHandler(object):
             self._isondemand = False
         else:
             if (attrvalue[self.node]['console.logging']['value'] not in (
-                'full', '', 'buffer')):
+                'full', '', 'memory')):
                 self._isondemand = True
             if (attrvalue[self.node]['console.logging']['value']) in ('none', 'memory'):
                 self._dologging = False