A couple of fixes to support zenoss 4.2.5

In ev_query there was a :history assignment, but according to the document, this has actually been deprecated and will generate an error on calls to zenoss.

When performing a login zenoss apparently throws a 302 redirect with Location set to /zport/dmd and not with a complete hostname, this makes httpclient very unhappy and further calls are in error. Prepending the zenoss_uri to the Location header will fix that issue.