Fix a couple of logcontext leaks

Use preserve_fn to correctly manage the logcontexts around things we don't want
to yield on.

synapse/api/auth.py

@@ -23,7 +23,7 @@ from synapse import event_auth
 from synapse.api.constants import EventTypes, Membership, JoinRules
 from synapse.api.errors import AuthError, Codes
 from synapse.types import UserID
-from synapse.util.logcontext import preserve_context_over_fn
+from synapse.util import logcontext
 from synapse.util.metrics import Measure
 
 logger = logging.getLogger(__name__)
@@ -209,8 +209,7 @@ class Auth(object):
                 default=[""]
             )[0]
             if user and access_token and ip_addr:
-                preserve_context_over_fn(
-                    self.store.insert_client_ip,
+                logcontext.preserve_fn(self.store.insert_client_ip)(
                     user=user,
                     access_token=access_token,
                     ip=ip_addr,

synapse/util/retryutils.py

@@ -12,7 +12,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
-
+import synapse.util.logcontext
 from twisted.internet import defer
 
 from synapse.api.errors import CodeMessageException
@@ -173,4 +173,5 @@ class RetryDestinationLimiter(object):
                     "Failed to store set_destination_retry_timings",
                 )
 
-        store_retry_timings()
+        # we deliberately do this in the background.
+        synapse.util.logcontext.preserve_fn(store_retry_timings)()