lav*,tests: remove several register_all calls

avdevice_register_all() is still required to register devices into
lavf (this is required due to lavd being somewhat of a hack).

Signed-off-by: Josh de Kock <josh@itanimul.li>

libavformat/tests/movenc.c

@@ -379,8 +379,6 @@ int main(int argc, char **argv)
         }
     }
 
-    av_register_all();
-
     md5 = av_md5_alloc();
     if (!md5)
         return 1;