test: Avoid focused host selector for pixel test

TestHostSwitching.testBasic does pixel tests of the host selector menu,
which is the top left element at position (0, 0). Current Chromium
changes behaviour to always focus that element, and it's fairly
stubborn.

To avoid pixel testing the focused (light-gray) variant, move the mouse
away first.

test/verify/check-shell-host-switching

@@ -183,6 +183,14 @@ class TestHostSwitching(testlib.MachineCase, HostSwitcherHelpers):
         b.wait_not_present("#nav-system.interact")
         b.set_layout("desktop")
 
+        # this looks different (focused) when the mouse is inside (default 0,0 possition), so move it away
+        # chromium is stubborn here, we *have* to move the real mouse, not just do this with synthetic MouseEvents
+        b.bidi("input.performActions", context=b.driver.context, actions=[{
+            "id": "move-away",
+            "type": "pointer",
+            "parameters": {"pointerType": "mouse"},
+            "actions": [{"type": "pointerMove", "x": 200, "y": 200, "origin": "viewport"}]
+        }])
         b.assert_pixels("#hosts-sel", "hosts-sel-closed")
 
         b.click("#hosts-sel button")