Change default local ovs connection timeout

Large number of flows can cause local ovs connection
timeout. Ultimately getting succeed will be better
than a retry or fullsync.

Related-Bug: #1813703
Related-Bug: #1813705
Related-Bug: #1813707
Related-Bug: #1813709

Change-Id: Ifa0608a7e131df3cad2f7727426720afce641a58
(cherry picked from commit 64ea642359)

neutron/conf/plugins/ml2/drivers/ovs_conf.py

@@ -85,11 +85,11 @@ ovs_opts = [
     cfg.PortOpt('of_listen_port', default=6633,
                 help=_("Port to listen on for OpenFlow connections. "
                        "Used only for 'native' driver.")),
-    cfg.IntOpt('of_connect_timeout', default=30,
+    cfg.IntOpt('of_connect_timeout', default=300,
                help=_("Timeout in seconds to wait for "
                       "the local switch connecting the controller. "
                       "Used only for 'native' driver.")),
-    cfg.IntOpt('of_request_timeout', default=10,
+    cfg.IntOpt('of_request_timeout', default=300,
                help=_("Timeout in seconds to wait for a single "
                       "OpenFlow request. "
                       "Used only for 'native' driver.")),

releasenotes/notes/change-of-default-timeout-b09d11683526e27d.yaml

@@ -0,0 +1,7 @@
+---
+other:
+  - |
+    In order to improve heavy load ovs agent restart success rate, instead
+    a retry or fullsync, the native driver ``of_connect_timeout`` and
+    ``of_request_timeout`` are now set to 300s. The value does not have side
+    effect for the regular pressure ovs agent.