Fix unit test failures

Author: yegappan

test/test_exit_only_window.vim

@@ -14,6 +14,7 @@ augroup END
 
 Tlist
 close
+sleep 50m
 
 call writefile(['Test_Tlist_Exit_OnlyWindow: FAIL'], 'test.log', 'a')
 augroup TaglistTest

test/unit_tests.vim

@@ -1909,6 +1909,7 @@ func Test_Tlist_Exit_OnlyWindow_tabpage()
   Tlist
   call assert_equal([2, 2], [tabpagenr(), winnr()])
   close
+  sleep 50m
   call assert_equal([1, 2], [tabpagenr(), winnr()])
   TlistClose
   let g:Tlist_Exit_OnlyWindow=0