Fix some looping_call calls which were broken in #3604

It turns out that looping_call does check the deferred returned by its
callback, and (at least in the case of client_ips), we were relying on this,
and I broke it in #3604.

Update run_as_background_process to return the deferred, and make sure we
return it to clock.looping_call.

1 files changed, 1 insertions, 1 deletions

diff --git a/synapse/groups/attestations.py b/synapse/groups/attestations.py

index 4216af0a27..b04f4234ca 100644
--- a/synapse/groups/attestations.py
+++ b/synapse/groups/attestations.py
@@ -153,7 +153,7 @@ class GroupAttestionRenewer(object):
         defer.returnValue({})
 
     def _start_renew_attestations(self):
-        run_as_background_process("renew_attestations", self._renew_attestations)
+        return run_as_background_process("renew_attestations", self._renew_attestations)
 
     @defer.inlineCallbacks
     def _renew_attestations(self):