patch 9.0.1012: tests may get stuck in buffer with swap file

Problem:    Tests may get stuck in buffer with swap file.
Solution:   Bail out when bwipe! doesn't get another buffer.

src/testdir/runtest.vim

@@ -368,7 +368,14 @@ func RunTheTest(test)
   " buffer, continue until we end up in an empty no-name buffer without a swap
   " file.
   while bufname() != '' || execute('swapname') !~ 'No swap file'
-    bwipe!
+    let bn = bufnr()
+
+    noswapfile bwipe!
+
+    if bn == bufnr()
+      " avoid getting stuck in the same buffer
+      break
+    endif
   endwhile
 
   " Check if the test has left any swap files behind.  Delete them before

src/version.c

@@ -695,6 +695,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1012,
 /**/
     1011,
 /**/