In order to enable image uploads in horizon we need to configure several
things in glance, namely cors. This change implements default overrides
allowing the system to provide for direct image uploads through horizon
which will greatly improve our usability, especially for new users.
Change-Id: I19f4027dd30b0ba22cbb195c676802ce908d3e8f
Closes-Bug: #1747684
Signed-off-by: Kevin Carter <kevin.carter@rackspace.com>