progress_page:Disable F2 key when starting installing RHEV-H

Previously progress page accepts F2 to drop to shell,if press F2 Key
repeated when starting installing RHEV-H, this action may cause install
RHEV-H failed.
Now disabled F2 key when starting installing RHEV-H, after finished
installing RHEV-H, and enabled F2 key again in progress page

Change-Id: Ia670fc848ce324033de72ec52a047d24e78e151c
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=981596
Signed-off-by: hadong <hadong0720@gmail.com>