Unreviewed, rolling out r168232.
https://bugs.webkit.org/show_bug.cgi?id=132543

broke ~15 tests on WK2 debug (Requested by kling on #webkit).

Reverted changeset:

"Shortcircuit shouldUseCredentialStorage callback"
https://bugs.webkit.org/show_bug.cgi?id=132308
http://trac.webkit.org/changeset/168232

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@168241 268f45cc-cd09-0410-ab3c-d52691b4dbfc