Hard coded path for mediainfo

[micolous]

There's a hard coded path to /usr/local/bin/mediainfo in autodetect_file.c:

https://github.com/Comcast/caption-inspector/blob/476326f08a43ce38ecd1ea58b8910d7015e80cac/src/utils/autodetect_file.c#L52

As a result, if you have installed mediainfo in another directory that is in the PATH (eg: /usr/bin), such as installing it via apt install mediainfo, caption-inspector won't find it.

The Docker build appears to work around this by moving the binary:

https://github.com/Comcast/caption-inspector/blob/476326f08a43ce38ecd1ea58b8910d7015e80cac/Dockerfile#L62

The easy fix is to change this to:

char* mediaInfoInvokeStr = "mediainfo";

But it may also need a fix-up for the Docker container which puts the binary elsewhere.