clean up portinstall::install_element, including removal of a check whose intent was unnecessary and whose implementation was incorrect
clean up portinstall::install_element, including removal of a check whose intent was unnecessary and whose implementation was incorrect

git-svn-id: 620571fa9b4bd0cbce9a0cf901e91ef896adbf27@51928 d073be05-634f-4543-b044-5fe20cf6d1d6

danchr/macports-base,neverpanic/macports-base,neverpanic/macports-base,macports/macports-base,danchr/macports-base,macports/macports-base