Fix special handling of a fake language code "tl".

My previous CL 92280cd3 [1] had a silly
mistake that "tl" is converted to "fil" but "tl_PH" is not.

  [1] I94f203bddceb9c87710cb187cc3cc0ee6d9092a5

With this CL, the compatibility rewrite-rule from "tl" to "fil" starts
working regardless of the existence of countly/variant subtags in locale
string.  So far the only affected platfrom is API Level 23.

Bug: 20696126
Change-Id: Ica9cd2baac002c406f92331aadd7725d7424046a