webadmin: Main tab presenter loading

- When clicking a main tab right after login the application
  would load the code fragments for all main tabs instead of
  just the one you clicked on. This patch fixes that issue and
  only the tab you selected is loaded.

Change-Id: I63695ad15cbd5633bb081f2f031fb31743886c14
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1155992
Signed-off-by: Alexander Wels <awels@redhat.com>