webadmin: import dialog doesnt open

Moving 'initSubTabLayoutPanel' call from the ctr to
'edit' method to make sure the model is already
initialized (importModel initialization is done on 'edit').

Change-Id: I1cbce0ba41b17d449d910c301e9cd8fd4193dc5d
Signed-off-by: Daniel Erez <derez@redhat.com>