http: Legacy versions of IIS redirect incorrectly

(And newer versions don't seem to like the legacy code). This patch uses a
`Refresh` header for IIS versions prior to 7.0 (included with Windows Vista
/ Server 2008). Starting with IIS 7.0, the Location header should be
properly handled by IIS.
Merge pull request #874 from greezybacon/issue/iis-refresh

http: Legacy versions of IIS redirect incorrectly

Reviewed-By: Peter Rotich <peter@osticket.com>