Correct get_home_path() for cases where WordPress is installed in a...

Correct get_home_path() for cases where WordPress is installed in a subdirectory called /wp/, previously it would match on /wp-admin instead of /wp causing an incorrect return path. Props SergeyBiryukov. Fixes #20449


git-svn-id: https://core.svn.wordpress.org/trunk@22800 1a063a9b-81f0-0310-95a4-ce76da25c4cd