The Picker of the ComboBox, has by default a maxHeight of 300 px. If the list of elements is bigger that 300 pixels, then a scrollbar will be added.
This behaviour was broken with ExtJS4, but now works correctly with ExtJS6.
This fixes the problem that this ComboGrid was displayed with an empty value
( similar the to the Keyboard Selection and Realm Selection in the login window)
An component id 'comment' is already defined for the column Comment of UserView.js causing here a conflict.
It seems ExtJS6 is more stringent about that than ExtJS4.
If the default activeTab is *undefined* and *not* null, activeTab defaults to 0,
so we don't need to set this explicitely.
dug from ExtJS tabPanel:
activeTab = me.activeTab !== null ? (me.activeTab || 0) : null;
Using ExtJS6 a browser refresh (F5) do not send the 'show' event which we use to display the store as it did with ExtJS4.
At the momment only for tabs inside the datacenter tabpanel, since node and lxc tabpanels are not yet in manager6/
