Don't call RefreshColumns() in directory_backing_store_unittest.cc.

Move "column deleted" checks from test case MigrateVersion85To86 to test
case ToCurrentVersion where they will execute after a RefreshColumns().

RefreshColumns() should not be called from MigrateVersionXToY test cases
because it will create in a metas table with all columns know to the
code (i.e. the latest version).

BUG=

Review URL: https://codereview.chromium.org/182683004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@254310 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 254310