patch 8.2.3440: recover test fails if there is an old swap file

Problem:    Recover test fails if there is an old swap file.
Solution:   Delete old swap files.
diff --git a/src/testdir/test_recover.vim b/src/testdir/test_recover.vim
index 6ef4376..9d25883 100644
--- a/src/testdir/test_recover.vim
+++ b/src/testdir/test_recover.vim
@@ -170,6 +170,12 @@
   call assert_match('Unable to read block 0 from .Xfile1.swp', msg)
   call assert_equal('Xfile1', @%)
   bw!
+
+  " make sure there are no old swap files laying around
+  for f in glob('.sw?', 0, 1)
+    call delete(f)
+  endfor
+
   " :recover from an empty buffer
   call assert_fails('recover', 'E305:')
   call delete('.Xfile1.swp')