fedabipkgdiff: Fix previous commit

In the previous commit, I wrongly assumed that all Brew koji session objects
have a an "opts" attribute.  Fixed thus.

	 * tools/fedabipkgdiff (Brew::__init__): Do not try to access the
	'opts' attribute on sessions that don't have any.

Signed-off-by: Dodji Seketeli <dodji@redhat.com>

tools/fedabipkgdiff

@@ -662,7 +662,8 @@ class Brew(object):
         # I am instructing the http client to avoid verifying SSL
         # certificates by default as some Koji server instance might
         # use self-signed certficates that can't be easily verified.
-        self.session.opts.setdefault('no_ssl_verify', True)
+        if (hasattr(self.session, 'opts')):
+            self.session.opts.setdefault('no_ssl_verify', True)
 
     @log_call
     def listRPMs(self, buildID=None, arches=None, selector=None):