Events panel is not refreshed when switching between machine tabs

While doing #429 (closed) I noticed that, unlike in case of app panels, when you open several machines panels and switch between them the events are not updated to the currently selected machine. In order to view events from the current machine one has to switch to the first (all machines) tab and then go back to the desired one. Another way is to refresh the page.

In order to reproduce:

• Start Stork demo
• Add two new machines, e.g. agent-kea-ha1 and agent-kea-ha2
• Click between agent-kea-ha1 and agent-kea-ha2 tabs. The events panel is not refreshed and is showing events specific to the other machine.
• Click on the Machines tab and go back. Now, events are properly displayed.