support/testing: weston: fix the weston shutdown test

Commit [1] "support/testing: improve weston test reliability" moved
out the wait time from the emulator (to run on the test controller).

While doing so, the sleep time which was initially _after_ the
"killall weston" invocation to in stop_weston() was incorrectly
moved before the command invocation. In this state, the test can
succeed on fast host computer running the test. But it will most
likely fail on an average computer.

This commit fixes this issue by moving the sleep time after
the command invocation.

[1] https://gitlab.com/buildroot.org/buildroot/-/commit/6561a5d773d8e159556e2b911b315e3b5a0b89b1

Signed-off-by: Julien Olivain <ju.o@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

support/testing/tests/package/test_weston.py

@@ -58,8 +58,8 @@ class TestWeston(infra.basetest.BRTest, GraphicsBase):
 
     def stop_weston(self):
         cmd = "killall weston"
-        time.sleep(3)
         self.assertRunOk(cmd)
+        time.sleep(3)
 
     def test_run(self):
         img = os.path.join(self.builddir, "images", "rootfs.cpio.gz")