http: don't bother making a copy of the options

Alternative to https://github.com/iojs/io.js/pull/592. The `options` object is never overwritten, so making a copy is not necessary.

This solves issues such as https://github.com/petkaantonov/urlparser/issues where the options object is created from a constructor.

PR-URL: https://github.com/iojs/io.js/pull/593


Reviewed-By: Stephen Belanger <admin@stephenbelanger.com>