webadmin: 'Comment' property of existing VM pool dialog editable

The problem was that the PoolEditPopupWidget.disableAllTabs(); disabled
all the widgets and the subsequent PoolEditPopupWidget.
enableEditPoolFields(object); did not enable it.

Fixed by adding the missing commentEditor.setEnabled(true);
to enableEditPoolFields

Change-Id: I9fe10ea813636a271e1663009d24b6def0072939
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1013699
Signed-off-by: Jakub Niedermertl <jniederm@redhat.com>