[log]: Change entry point name of logging plugin
[log]: Change entry point name of logging plugin

The name ('logapi') seems redundant 'api' and it looks inconsistent
with entry point name of logging agent extension ('log') and
LoggingPlugin class[1]. So this patch change 'logapi' to 'log' to
make it look consistent.

[1] https://github.com/openstack/neutron/blob/master/neutron/services/logapi/logging_plugin.py#L27

Change-Id: I57d0b86823670a1dc5d116d98059993c802ef86c
Partially-implements: blueprint security-group-logging
Related-Bug: #1468366

openstack/neutron,openstack/neutron,mahak/neutron,mahak/neutron,noironetworks/neutron,huntxu/neutron,huntxu/neutron,noironetworks/neutron,openstack/neutron,mahak/neutron