Register fatal_deprecations before use

The keystone.tests.unit.test_backend_sql.DeprecatedDecorators
tests would fail when run individually with an error

 oslo_config.cfg.NoSuchOptError: no such option: fatal_deprecations

This is because the way that fatal_deprecations gets registered is
when versionutils.report_deprecated_feature() is called.

The fix is to call versionutils.report_deprecated_feature() before
trying to set the fatal_deprecations option.

Change-Id: I6ad2dd0a47f00ea2ba05d587e0291230e789f057
Closes-Bug: 1474069

keystone/tests/unit/test_backend_sql.py

@@ -20,6 +20,7 @@ import mock
 from oslo_config import cfg
 from oslo_db import exception as db_exception
 from oslo_db import options
+from oslo_log import log
 from oslo_log import versionutils
 from six.moves import range
 import sqlalchemy
@@ -939,6 +940,14 @@ class SqlCredential(SqlTests):
 
 class DeprecatedDecorators(SqlTests):
 
+    def setUp(self):
+        super(DeprecatedDecorators, self).setUp()
+
+        # The only reason this is here is because report_deprecated_feature()
+        # registers the fatal_deprecations option which these tests use.
+        versionutils.report_deprecated_feature(
+            log.getLogger(__name__), 'ignore this message')
+
     def test_assignment_to_role_api(self):
         """Test that calling one of the methods does call LOG.deprecated.