Update third party submodule setup (#2132)

Summary:
update the logic for initializing and updating submodule in setup, now that we have more than one submodule

Pull Request resolved: https://github.com/pytorch/audio/pull/2132

Reviewed By: mthrok

Differential Revision: D33410039

Pulled By: carolineechen

fbshipit-source-id: 6e18ec2904a01efb2f753f65345de063218c0b9b

setup.py

@@ -123,8 +123,7 @@ def _fetch_archives(src):
 
 
 def _fetch_third_party_libraries():
-    if not (ROOT_DIR / "third_party" / "kaldi" / "submodule" / "CMakeLists.txt").exists():
-        _init_submodule()
+    _init_submodule()
     if os.name != "nt":
         _fetch_archives(_parse_sources())