Fixes crashes with android scene updates (#1177)
Fixes crashes with android scene updates (#1177)

- Cause was a bad JNI environment on startUrlRequest
- Fixed with attaching current url thread to the jni and grabbing jniEnvironment from it. (Apparently we already had a
wrapper class doing this, which was not used here)

Fixes #978
quitejonny/tangram-es,cleeus/tangram-es,quitejonny/tangram-es,cleeus/tangram-es,quitejonny/tangram-es,tangrams/tangram-es,tangrams/tangram-es,tangrams/tangram-es,tangrams/tangram-es,quitejonny/tangram-es,cleeus/tangram-es,quitejonny/tangram-es,cleeus/tangram-es,cleeus/tangram-es,tangrams/tangram-es,cleeus/tangram-es,quitejonny/tangram-es,tangrams/tangram-es,tangrams/tangram-es