patch 9.0.0415: on MS-Windows some tests are flaky

Problem:    On MS-Windows some tests are flaky.
Solution:   Add sleeps, disable swapfile, mark test as flaky. (Ken Takata,
            closes #11082)
diff --git a/src/testdir/test_autocmd.vim b/src/testdir/test_autocmd.vim
index 669089d..3370190 100644
--- a/src/testdir/test_autocmd.vim
+++ b/src/testdir/test_autocmd.vim
@@ -763,6 +763,7 @@
 
   call writefile(content, 'Xvimrc', 'D')
   call system(GetVimCommand('Xvimrc') .. ' --not-a-term --noplugins -S Session.vim -c cq')
+  sleep 50m
   let errors = join(readfile('Xerrors'))
   call assert_match('E814:', errors)
 
diff --git a/src/testdir/test_buffer.vim b/src/testdir/test_buffer.vim
index 489926d..9387b5f 100644
--- a/src/testdir/test_buffer.vim
+++ b/src/testdir/test_buffer.vim
@@ -375,6 +375,7 @@
 func Test_buffer_scheme()
   CheckMSWindows
 
+  set noswapfile
   set noshellslash
   %bwipe!
   let bufnames = [
@@ -397,6 +398,7 @@
   endfor
 
   set shellslash&
+  set swapfile&
 endfunc
 
 " this was using a NULL pointer after failing to use the pattern
diff --git a/src/testdir/test_bufline.vim b/src/testdir/test_bufline.vim
index f3502a3..c592877 100644
--- a/src/testdir/test_bufline.vim
+++ b/src/testdir/test_bufline.vim
@@ -83,6 +83,7 @@
   endif
   call writefile(['call setline(1, "Hello")', 'silent w Xtest', 'q!'], 'Xscript', 'D')
   call system(cmd)
+  sleep 50m
   call assert_equal(['Hello'], readfile('Xtest'))
 
   call delete('Xtest')
diff --git a/src/testdir/test_profile.vim b/src/testdir/test_profile.vim
index 340048e..47ff2a2 100644
--- a/src/testdir/test_profile.vim
+++ b/src/testdir/test_profile.vim
@@ -53,6 +53,7 @@
     \ . ' -c "qall!"')
   call assert_equal(0, v:shell_error)
 
+  sleep 50m
   let lines = readfile('Xprofile_func.log')
 
   " - Foo1() is called 3 times but should be reported as called twice
diff --git a/src/testdir/test_shell.vim b/src/testdir/test_shell.vim
index a6aa10e..1ed4c5e 100644
--- a/src/testdir/test_shell.vim
+++ b/src/testdir/test_shell.vim
@@ -5,6 +5,11 @@
 source shared.vim
 
 func Test_shell_options()
+  if has('win32')
+    " FIXME: This test is flaky on MS-Windows.
+    let g:test_is_flaky = 1
+  endif
+
   " The expected value of 'shellcmdflag', 'shellpipe', 'shellquote',
   " 'shellredir', 'shellxescape', 'shellxquote' for the supported shells.
   let shells = []
diff --git a/src/testdir/test_undo.vim b/src/testdir/test_undo.vim
index a2f3c01..61cab68 100644
--- a/src/testdir/test_undo.vim
+++ b/src/testdir/test_undo.vim
@@ -335,6 +335,11 @@
 endfunc
 
 func Test_undofile_earlier()
+  if has('win32')
+    " FIXME: This test is flaky on MS-Windows.
+    let g:test_is_flaky = 1
+  endif
+
   " Issue #1254
   " create undofile with timestamps older than Vim startup time.
   let t0 = localtime() - 43200
diff --git a/src/testdir/test_viminfo.vim b/src/testdir/test_viminfo.vim
index c3ec5b0..7101727 100644
--- a/src/testdir/test_viminfo.vim
+++ b/src/testdir/test_viminfo.vim
@@ -722,6 +722,7 @@
 endfunc
 
 func Test_viminfo_oldfiles()
+  set noswapfile
   let v:oldfiles = []
   let lines = [
 	\ '# comment line',
@@ -765,6 +766,7 @@
   call assert_equal("/tmp/another.txt", expand("%"))
   bwipe
   delmark E
+  set swapfile&
 endfunc
 
 " Test for storing and restoring buffer list in 'viminfo'