patch 8.1.2261: with modifyOtherKeys set 'noesckeys' doesn't work

Problem:    With modifyOtherKeys set 'noesckeys' doesn't work. (James McCoy)
Solution:   Disable modifyOtherKeys while in Insert mode when 'noesckeys' is
            set. (closes #5180)
diff --git a/src/testdir/test_edit.vim b/src/testdir/test_edit.vim
index 6ee5848..18846f6 100644
--- a/src/testdir/test_edit.vim
+++ b/src/testdir/test_edit.vim
@@ -1495,3 +1495,22 @@
   set backspace&
   bwipe!
 endfunc
+
+func Test_edit_noesckeys()
+  new
+
+  " <Left> moves cursor when 'esckeys' is set
+  exe "set t_kl=\<Esc>OD"
+  set esckeys
+  call feedkeys("axyz\<Esc>ODX", "xt")
+  call assert_equal("xyXz", getline(1))
+
+  " <Left> exits Insert mode when 'esckeys' is off
+  set noesckeys
+  call setline(1, '')
+  call feedkeys("axyz\<Esc>ODX", "xt")
+  call assert_equal(["DX", "xyz"], getline(1, 2))
+
+  bwipe!
+  set esckeys
+endfunc