http_static: clean up http redirect generation

http_static: clean up http redirect generation

Don't redirect to "favicon.ico/index.html" if you can't find
"favicon.ico".

If asked to serve up a nonexistent path, see if the path ends with a
known suffix: ".jpg, .html, .ico" etc. If it does, flunk the request
on the spot: "Error 404 Not Found." Do not issue a redirect.

This change will not break the obvious corner case: if the browser
asks for "its_a_dir.mp3/index.html" - and the file exists - the server
will produce it.

Type: improvement

Signed-off-by: Dave Barach <dave@barachs.net>
Change-Id: I91aad90be05b98ba2b40e240d13d71816aed4526