Only log IDs of callbacks in debug message
Only log IDs of callbacks in debug message

Logging the ID of the callback should be enough
since the ID contains the path to the callback.

Before:
Notify callbacks
[('neutron.services.segments.db._update_segment_host_mapping_for_agent-8784700722903',
  <function _update_segment_host_mapping_for_agent at 0x7fd58f74ed70>)]
for agent, after_create _notify_loop"

After:
Notify callbacks
['neutron.services.segments.db._update_segment_host_mapping_for_agent-8784700722903']
for agent, after_create _notify_loop"

TrivialFix

Change-Id: Ice15c89c7a6288af5a0385df9e3e74e9d9d6f977

openstack/neutron-lib,openstack/neutron-lib,openstack/neutron-lib,openstack/neutron-lib