Fix TLS 1.2 support for Android 4.4.x versions

[geriux]

The current implementation to support TLS 1.2 in Android 4.4.x versions stopped working for us and we had to change it to this approach. It'd be great to have it merge if anyone else is having issues with this as well.

[Traviskn]

I am not familiar enough with this particular part of the code to be comfortable reviewing and merging. Is there anyone who can review this PR and/or confirm that they have tested it works without breaking anything?

[mikehardy]

For what it's worth, this looks correct to me and it would be great to have as I have an out-of-play-store APK downloader that uses react-native-fs (which also mishandles Android 4.x TLS) and I'm currently only able to patch it by using Play Services because it really has to be done at this layer.

My read on the code and the related okhttp github forum makes me feel this should work.

A test plan would be to use an Android 4.x emulator (none of the old emulators have play services, so you know you've got a busted TLS implementation there...), load this code, and try to fetch a file from github's raw-content URLs

It's similar to my testing block here: https://github.com/mikehardy/react-native-update-apk#testing

And a file you can use to test, could just be https://raw.githubusercontent.com/joltup/rn-fetch-blob/master/README.md