webadmin: Reset status panel on redraw

A recent regression caused status messages to linger on past a
redraw. This is changed so only warning messages survive
redraws.

Change-Id: Ic110c6dd4198a03c3274dfbb9fe39a8687a9861a
Bug-Url: https://bugzilla.redhat.com/1115109
Signed-off-by: Lior Vernia <lvernia@redhat.com>