webadmin,userportal: Remove '__gwt_historyFrame' iframe

This iframe is needed only for IE6-7 support. Since we support
IE9+, having this iframe within GWT host page is just redundant.

Change-Id: I5b5946a536fbc441cb6dca75f8dc36760164b534
Signed-off-by: Vojtech Szocs <vszocs@redhat.com>