patch 8.0.0480: the remote_peek() test fails on MS-Windows

Problem:    The remote_peek() test fails on MS-Windows.
Solution:   Check for pending messages. Also report errors in the first run if
            a flaky test fails twice.
diff --git a/src/testdir/runtest.vim b/src/testdir/runtest.vim
index b896443..1d694b5 100644
--- a/src/testdir/runtest.vim
+++ b/src/testdir/runtest.vim
@@ -250,8 +250,17 @@
     call add(s:messages, 'Found errors in ' . s:test . ':')
     call extend(s:messages, v:errors)
     call add(s:messages, 'Flaky test failed, running it again')
+    let first_run = v:errors
+
     let v:errors = []
     call RunTheTest(s:test)
+    if len(v:errors) > 0
+      let second_run = v:errors
+      let v:errors = ['First run:']
+      call extend(v:errors, first_run)
+      call add(v:errors, 'Second run:')
+      call extend(v:errors, second_run)
+    endif
   endif
 
   call AfterTheTest()