patch 8.0.1271: still too many old style tests

Problem:    Still too many old style tests.
Solution:   Convert a few more tests to new style. (Yegappan Lakshmanan,
            closes #2290)

src/testdir/test_ins_complete.vim

@@ -2,6 +2,11 @@
 " Test for insert expansion
 func Test_ins_complete()
   edit test_ins_complete.vim
+  " The files in the current directory interferes with the files
+  " used by this test. So use a separate directory for the test.
+  call mkdir('Xdir')
+  cd Xdir
+
   set ff=unix
   call writefile(["test11\t36Gepeto\t/Tag/",
 	      \ "asd\ttest11file\t36G",
@@ -89,6 +94,8 @@ func Test_ins_complete()
   call delete('Xtest11.two')
   call delete('Xtestdata')
   set cpt& cot& def& tags& tagbsearch& hidden&
+  cd ..
+  call delete('Xdir', 'rf')
 endfunc
 
 func Test_omni_dash()