patch 8.0.0291: Visual block insertion does not insert in all lines

Problem:    Visual block insertion does not insert in all lines.
Solution:   Don't bail out of insert too early. Add a test. (Christian
            Brabandt, closes #1290)

src/testdir/test_visual.vim

@@ -23,3 +23,16 @@ func Test_dotregister_paste()
   call assert_equal('hello world world', getline(1))
   q!
 endfunc
+
+func Test_Visual_ctrl_o()
+  new
+  call setline(1, ['one', 'two', 'three'])
+  call cursor(1,2)
+  set noshowmode
+  set tw=0
+  call feedkeys("\<c-v>jjlIa\<c-\>\<c-o>:set tw=88\<cr>\<esc>", 'tx')
+  call assert_equal(['oane', 'tawo', 'tahree'], getline(1, 3))
+  call assert_equal(88, &tw)
+  set tw&
+  bw!
+endfu