webadmin, userportal: Resize dialogs to fit the screen in 1024x768 resolution

Resized the VM run once dialog and VM/Template import dialogs to fit the screen
in 1024x768 resolution

related to https://bugzilla.redhat.com/879324

Change-Id: I126c65ebe1adcd490a09d0fb8961118c0afbde30
Signed-off-by: Tal Nisan <tnisan@redhat.com>