webadmin: tabbar position off on login

- Fixed issue where if the width of the system tree was
  not the default, the tabbar would be in the wrong
  position.

Change-Id: I63b6b48e15fbb7cf4a5a76865609c1fc5f1a14a9
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1071339
Signed-off-by: Alexander Wels <awels@redhat.com>