v4l2: Set O_CLOEXEC on the device fd
v4l2: Set O_CLOEXEC on the device fd

This is needed to make sure that child processes don't inherit the video
device fd which can cause problems with some drivers.

Kurento/gst-plugins-good,Kurento/gst-plugins-good,GStreamer/gst-plugins-good,hizukiayaka/gst-plugins-good,GrokImageCompression/gst-plugins-good,hizukiayaka/gst-plugins-good,stfl/gst-plugins-good,StreamUtils/gst-plugins-good,hizukiayaka/gst-plugins-good,Kurento/gst-plugins-good,pexip/gst-plugins-good,stfl/gst-plugins-good,hizukiayaka/gst-plugins-good,GrokImageCompression/gst-plugins-good,StreamUtils/gst-plugins-good,pexip/gst-plugins-good,pexip/gst-plugins-good,StreamUtils/gst-plugins-good,StreamUtils/gst-plugins-good,GStreamer/gst-plugins-good,GrokImageCompression/gst-plugins-good,pexip/gst-plugins-good,GStreamer/gst-plugins-good,GStreamer/gst-plugins-good,stfl/gst-plugins-good,GrokImageCompression/gst-plugins-good,pexip/gst-plugins-good,Kurento/gst-plugins-good,Kurento/gst-plugins-good,stfl/gst-plugins-good