Fix MockHttpRequest always returning M_UNKNOWN errcode in testing
Fix MockHttpRequest always returning M_UNKNOWN errcode in testing

matrix-org/synapse,matrix-org/synapse,matrix-org/synapse,TribeMedia/synapse,TribeMedia/synapse,matrix-org/synapse,TribeMedia/synapse,matrix-org/synapse,TribeMedia/synapse,matrix-org/synapse,TribeMedia/synapse