Site Icon: Make sure that we don't pass the path to the file name, Needs testing on windows server
Site Icon: Make sure that we don't pass the path to the file name

See dfe7bf17b0f8186fa291e409e08e93237a90b5e7
Site Icon: Update to also generate the metadata properly again

The previous fix broke the wp_generate_attachment_metadata step since
it passed in the wrong file path.
Merge pull request #1380 from Automattic/fix/1327-site-icon-path-issue

Fixes #1327 site icon path issue for windows installs.