Fix incorrect status handling at staticweb

Staticweb middleware always searchs html
for error response when response status code
is not redirect.
It causes swift to return error response
even if the request succeeded.
(e.g. When finding index.html with 200,
      staticweb returns 200error.html
      if it exist)

This patch modifies the constraint on response
status and fix bug 1204319.

Fixes bug #1204319.

Change-Id: Ib83c303917da7fb94999f2d4d35063b450d0e992
Merge "Fix incorrect status handling at staticweb"