patch 8.0.1329: when a flaky test fails it also often fails the second time

Problem:    When a flaky test fails it also often fails the second time.
Solution:   Sleep a couple of seconds before the second try.

src/testdir/runtest.vim

@@ -286,6 +286,10 @@ for s:test in sort(s:tests)
     call add(s:messages, 'Flaky test failed, running it again')
     let first_run = v:errors
 
+    " Flakiness is often caused by the system being very busy.  Sleep a couple
+    " of seconds to have a higher chance of succeeding the second time.
+    sleep 2
+
     let v:errors = []
     call RunTheTest(s:test)
     if len(v:errors) > 0

src/version.c

@@ -771,6 +771,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1329,
 /**/
     1328,
 /**/