Follow redirects from non-leaders in Marathon 1.7 (#595)

Marathon 1.7.x returns a 302 redirect response from a non-leader. So we make sure Marathon-lb can follow it to the leader.

Related Marathon JIRA card: https://jira.mesosphere.com/projects/MARATHON/issues/MARATHON-7178

Fixes #594

utils.py

@@ -158,6 +158,11 @@ def __init__(self, url, auth, verify):
         self.curl.setopt(pycurl.CONNECTTIMEOUT, 10)
         self.curl.setopt(pycurl.WRITEDATA, self.received_buffer)
 
+        # Marathon >= 1.7.x returns 30x responses for /v2/events responses
+        # when they're coming from a non-leader. So we follow redirects.
+        self.curl.setopt(pycurl.FOLLOWLOCATION, True)
+        self.curl.setopt(pycurl.MAXREDIRS, 1)
+
         # The below settings are to prevent the connection from hanging if the
         # connection breaks silently. Since marathon-lb only listens, silent
         # connection failure results in marathon-lb waiting infinitely.