Don't raise error when removing not existing IP address

When privileged delete_ip_address function is called to delete
IP address which is already not configured on device, it should
not fail with any error.

Conflicts:
    neutron/tests/functional/agent/linux/test_ip_lib.py

Change-Id: I9247ac899a76e5d9a2962d2cb81279f2d6f16c0b
Closes-Bug: #1757259
(cherry picked from commit bbe1bac3f7)

neutron/privileged/agent/linux/ip_lib.py

@@ -139,12 +139,21 @@ def add_ip_address(ip_version, ip, prefixlen, device, namespace, scope,
 @privileged.default.entrypoint
 def delete_ip_address(ip_version, ip, prefixlen, device, namespace):
     family = _IP_VERSION_FAMILY_MAP[ip_version]
-    _run_iproute_addr("delete",
-                      device,
-                      namespace,
-                      address=ip,
-                      mask=prefixlen,
-                      family=family)
+    try:
+        _run_iproute_addr("delete",
+                          device,
+                          namespace,
+                          address=ip,
+                          mask=prefixlen,
+                          family=family)
+    except NetlinkError as e:
+        # when trying to delete a non-existent IP address, pyroute2 raises
+        # NetlinkError with code EADDRNOTAVAIL (99, 'Cannot assign requested
+        # address')
+        # this shouldn't raise an error
+        if e.code == errno.EADDRNOTAVAIL:
+            return
+        raise
 
 
 @privileged.default.entrypoint