Stop using get_blogaddress_by_domain() when updating the siteurl/homeurl from the network admin.

props jeremyfelt, SergeyBiryukov.
fixes #18242. see #25235.


git-svn-id: http://develop.svn.wordpress.org/trunk@25261 602fd350-edb4-49c9-b593-d223f7449a82