Fix logic for camera check. Still run the test if webcam is found

TBR: phoglund@webrtc.org
No-Try: True
Bug: chromium:755660
Change-Id: Iea1ae4a599a644aca18181f68fe155a659163766
Reviewed-on: https://webrtc-review.googlesource.com/77426
Commit-Queue: Oleh Prypin <oprypin@webrtc.org>
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#23286}

tools_webrtc/ensure_webcam_is_running.py

@@ -110,13 +110,14 @@ def _ForcePythonInterpreter(cmd):
 
 
 def Main(argv):
-  if IsWebCamRunning():
-    return 0
-  if not StartWebCam():
-    return 1
+  if not IsWebCamRunning():
+    if not StartWebCam():
+      return 1
 
   if argv:
     return subprocess.call(_ForcePythonInterpreter(argv))
+  else:
+    return 0
 
 
 if __name__ == '__main__':