Use get_snmp_session_for_profile() in Arnold

Arnold mostly uses PortAdmin management handlers, except for when
changing the ifAdminStatus value of a port.

This lets the get_snmp_session_for_profile() utility function set up
these SNMP sessions instead, so that even SNMPv3 sessions will be
supported.

python/nav/arnold.py

@@ -40,6 +40,7 @@
 from nav.Snmp.errors import AgentError
 import nav.bitvector
 import nav.buildconf
+from nav.Snmp.profile import get_snmp_session_for_profile
 from nav.config import find_config_file
 from nav.errors import GeneralException
 from nav.models.arnold import Identity, Event
@@ -464,11 +465,7 @@ def change_port_status(action, identity):
     if not profile:
         raise NoReadWriteManagementProfileError
 
-    agent = nav.Snmp.Snmp(
-        host=netbox.ip,
-        community=profile.snmp_community,
-        version=profile.snmp_version,
-    )
+    agent = get_snmp_session_for_profile(profile)(host=netbox.ip)
 
     # Disable or enable based on input
     try: