patch 9.0.1034: reporting swap file when windows are split

Problem:    Reporting swap file when windows are split.
Solution:   Close extra windows after running a test.

src/testdir/runtest.vim

@@ -365,6 +365,11 @@ func RunTheTest(test)
   call add(s:messages, message)
   let s:done += 1
 
+  " close any split windows
+  while winnr('$') > 1
+    bwipe!
+  endwhile
+
   " May be editing some buffer, wipe it out.  Then we may end up in another
   " buffer, continue until we end up in an empty no-name buffer without a swap
   " file.