webadmin: refresh the Session sub-tab of vm

When select the Session sub-tab of a vm, if press F5
to refresh the web page, it displays a blank page.This
patch resolve the problem, it will display Virtual Machines
source tab.

Change-Id: I71d2e7b4c43b841bcdf05ec549efe50cbc9b4bda
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1104423
Signed-off-by: Ma Like <like.ma@cs2c.com.cn>