Fix save_chyrons.php's directory error

[waldoj]

This is a show-stopper:

# php ../bin/save_chyrons.php "$VIDEO_ID"
PHP Warning:  scandir(/home/ubuntu/video-processor/bin/../video/video/senate/floor/20180117/): failed to open dir: No such file or directory in /home/ubuntu/video-processor/bin/save_chyrons.php on line 111
PHP Warning:  scandir(): (errno 2): No such file or directory in /home/ubuntu/video-processor/bin/save_chyrons.php on line 111
PHP Warning:  Invalid argument supplied for foreach() in /home/ubuntu/video-processor/bin/save_chyrons.php on line 114

Looks like the video path is the faux one from the database. That's gonna need some rethinking.

In this case, we can get the video path from metadata.json.