Put a close button on the ping page

Even though the ping page was a normal plugin, switching back to
the regular list of plugins was unintuitive. Add a close button
so users can switch back either way.

Change-Id: I5b925443414df7e538310110e4b7a16d4244fcfd
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1083077
Signed-off-by: Ryan Barry <rbarry@redhat.com>