Migrate to oslo.log

It's mostly a matter of changing imports to a new location.

Non-obvious changes needed:
* pass overwrite= argument to oslo_context since oslo.log reads context
  from its thread local store and not local.store from incubator
* don't store context at local.store now that there is no code that
  would consume it
* LOG.deprecated() -> versionutils.report_deprecated_feature()
* dropped LOG.audit check from hacking rule since now the method does
  not exist
* WritableLogger is now located in oslo_log.loggers

Dropped log module from the tree. Also dropped local module that is now
of no use (and obsolete, as per oslo team).

Added versionutils back to openstack-common.conf since now we use the
module directly from neutron code and not just as a dependency of some
other oslo-incubator module.

Note: tempest tests are expected to be broken now, so instead of fixing
all the oslo.log related issues for the subtree in this patch, I only
added TODOs with directions for later fix.

Closes-Bug: #1425013
Change-Id: I310e059a815377579de6bb2aa204de168e72571e
diff --git a/neutron/tests/tempest/common/isolated_creds.py b/neutron/tests/tempest/common/isolated_creds.py
index 41d7390..e4b0b08 100644
--- a/neutron/tests/tempest/common/isolated_creds.py
+++ b/neutron/tests/tempest/common/isolated_creds.py
@@ -13,6 +13,7 @@
 #    under the License.
 
 import netaddr
+from oslo_log import log as logging
 from tempest_lib import exceptions as lib_exc
 
 from neutron.tests.api.contrib import clients
@@ -20,7 +21,6 @@
 from neutron.tests.tempest.common.utils import data_utils
 from neutron.tests.tempest import config
 from neutron.tests.tempest import exceptions
-from neutron.openstack.common import log as logging
 
 CONF = config.CONF
 LOG = logging.getLogger(__name__)