test: Robustify file download checks

- We only want to look at fully downloaded files, but in some
  situations the tests would be fast enough to catch Firefox's *.part
  file before it gets renamed to the real name. Ignore those.

- Bring back the wait for the file be of the expected size. This seems
  to be necessary on Chromium in order to not look at partial files.

- Remove the downloaded file so that the next check will not pick it
  up by accident. The one test with that calls waitViewerDownload
  twice (testExternalConsoleMultiHost) does it with exactly the same
  arguments and will pass if the second call looks at the file from
  the first call.

test/check-machines-consoles

@@ -38,6 +38,8 @@ class TestMachinesConsoles(machineslib.VirtualMachinesCase):
         if content is not None:
             self.assertEqual(filepath.read_text(), content)
 
+        os.unlink(filepath)
+
     def waitViewerDownload(self, kind, host, port=5900):
         self.browser.allow_download()
         self.browser.click(".pf-v5-c-console__remote-viewer-launch-vv")  # "Launch Remote Viewer" button
@@ -54,13 +56,17 @@ fullscreen=0
         # viewer file as a randomly generated file while chromium as
         # "download". As we want to download this as "$vmName.vv" in the end
         # work around the issue for now.
+
+        def ready_downloads():
+            return list(filter(lambda p: not p.endswith(".part"), os.listdir(self.browser.driver.download_dir)))
+
         if self.browser.browser == "chromium":
             fname = "download"
         else:
-            testlib.wait(lambda: len(os.listdir(self.browser.driver.download_dir)) == 1)
-            fname = os.listdir(self.browser.driver.download_dir)[0]
+            testlib.wait(lambda: len(ready_downloads()) == 1)
+            fname = ready_downloads()[0]
 
-        self.waitDownloadFile(fname, content=content)
+        self.waitDownloadFile(fname, content=content, expected_size=len(content))
 
     @testlib.skipImage('SPICE not supported on RHEL', "rhel-*", "centos-*")
     def testExternalConsole(self):