Dragonflow: increase timeout for fullstack jobs

[1] added some extra time to devstack setup in Dragonflow's tests due to
compilation of openvswitch, causing our jobs to time out occasionally.
Adding extra 15 minutes of grace.

[1] - https://review.openstack.org/#/c/465524

Change-Id: I864936a74987bdd544fa48bbf38e231d91eb2b64

jenkins/jobs/dragonflow.yaml

@@ -96,7 +96,7 @@
 
     wrappers:
       - build-timeout:
-          timeout: 150
+          timeout: 165
       - timestamps
 
     builders:
@@ -158,7 +158,7 @@
 
     wrappers:
       - build-timeout:
-          timeout: 150
+          timeout: 165
       - timestamps
 
     builders: