New contributor looking to patch memory leak on an open issue

[Murali Aniruddhan]

Hi,

I am a new contributor looking forward to contribute to the coturn project :).

I came across the following open issue here on this link: https://github.com/coturn/coturn/issues/1368

It is a leaksanitizer report which detects a leak that happens on make check.

I was able to reproduce the bug on running `make check` and was able to generate a patch for it. The leak happens within function check_oauth. Basically the variable base64encoded_ltp is allocated within base64_encode however it is not deallocated within the coming loop. I have a model patch and I was wondering if I can merge the same. The diff from commit da332ed9e718129d30efc467402d750e3c0fa9a3 is attached as a file below. I was able to verify that after the patch, the leak no longer occurs through leaksanitizer (and there is no double free for that matter)

 Let me know if this is a good patch! I am eager to become a regular contributor to this repository :)

Regards,

Aniruddhan