Avoid that running tests changes viminfo.

src/testdir/test29.in

@@ -4,7 +4,7 @@ Test for joining lines and marks in them
  and with 'cpoptions' flag 'j' set or not
 
 STARTTEST
-:set nocompatible
+:set nocompatible viminfo+=nviminfo
 :set nojoinspaces
 :set cpoptions-=j
 /firstline/

src/testdir/test72.in

@@ -6,7 +6,8 @@ STARTTEST
 :so small.vim
 :"
 :" Test 'undofile': first a simple one-line change.
-:set nocp ul=100 undofile nomore
+:set nocompatible viminfo+=nviminfo
+:set ul=100 undofile nomore
 :e! Xtestfile
 ggdGithis is one line:set ul=100
 :s/one/ONE/