Revert "[L3][HA] Retry when setting HA router GW status."

In short this patch can cause the privsep reader thread to
die resulting in the l3 agent getting stuck and e.g. not
processing any router updates. See related LP bug for full
explanation.

Closes-Bug: #1927868

This reverts commit 662f483120.

Change-Id: Ide7e9771d08eb623dd75941e425813d9b857b4c6
(cherry picked from commit 344fc0c8d2)

neutron/agent/l3/ha_router.py

@@ -537,11 +537,8 @@ class HaRouter(router.RouterInfo):
         if ex_gw_port_id:
             interface_name = self.get_external_device_name(ex_gw_port_id)
             ns_name = self.get_gw_ns_name()
-            if (not self.driver.set_link_status(
-                    interface_name, namespace=ns_name, link_up=link_up) and
-                    link_up):
-                LOG.error('Gateway interface for router %s was not set up; '
-                          'router will not work properly', self.router_id)
+            self.driver.set_link_status(interface_name, ns_name,
+                                        link_up=link_up)
             if link_up and set_gw:
                 preserve_ips = self.get_router_preserve_ips()
                 self._external_gateway_settings(ex_gw_port, interface_name,

neutron/agent/linux/interface.py

@@ -324,20 +324,14 @@ class LinuxInterfaceDriver(object):
 
     def set_link_status(self, device_name, namespace=None, link_up=True):
         ns_dev = ip_lib.IPWrapper(namespace=namespace).device(device_name)
-        try:
-            utils.wait_until_true(ns_dev.exists, timeout=3)
-        except utils.WaitTimeout:
-            LOG.debug('Device %s may have been deleted concurrently',
-                      device_name)
-            return False
-
+        if not ns_dev.exists():
+            LOG.debug("Device %s may concurrently be deleted.", device_name)
+            return
         if link_up:
             ns_dev.link.set_up()
         else:
             ns_dev.link.set_down()
 
-        return True
-
 
 class NullDriver(LinuxInterfaceDriver):
     def plug_new(self, network_id, port_id, device_name, mac_address,