Don't use FOLLY_TLS on Android

Don't use FOLLY_TLS on Android

Summary:
emutls as far as StaticMeta needs to use it is broken on
Android as well due to unspecified pthread_key cleanup order between the
emulated __thread and our manual uses of it. Use the alternative that we
use on __APPLE__ there as well.

Test Plan: compiled and ran consuming code on Android

Reviewed By: dancol@fb.com

Subscribers: fma, shikong, kmdent, benyluo, ranjeeth, subodh, folly-diffs@

FB internal diff: D1760569

Tasks: 5265754, 5907613

Signature: t1:1760569:1419955865:afe8f35dadda85393492ac9331e9f62a74f4fdad