webadmin: ApplicationMode - fix system tree filtering

- DataCenters, Providers and Provider type nodes will be visible
in system tree only if the ApplicationMode supports Virt.

- Modified the system tree filtering to add the grand child items
if all immediate child items are not visible.

Change-Id: I7969eab70929d8206f217a226b519b1fd14619b7
Signed-off-by: Kanagaraj M <kmayilsa@redhat.com>