patch 8.0.0613: the conf filetype is used before ftdetect from packages

Problem:    The conf filetype detection is done before ftdetect scripts from
            packages that are added later.
Solution:   Add the FALLBACK argument to :setfiletype. (closes #1679,
            closes #1693)
diff --git a/src/testdir/test_alot.vim b/src/testdir/test_alot.vim
index e961e99..fec2271 100644
--- a/src/testdir/test_alot.vim
+++ b/src/testdir/test_alot.vim
@@ -16,6 +16,7 @@
 source test_feedkeys.vim
 source test_file_perm.vim
 source test_fileformat.vim
+source test_filetype.vim
 source test_filter_cmd.vim
 source test_filter_map.vim
 source test_findfile.vim