muster release v5.43.4

A call to a backend that is reconnecting is no longer answered server not found. Three failed health probes move a server to Failed with a reconnect due, and the aggregator removed its registry entry until the reconnect registered it again; a call in that window, typically while the backend’s only pod is replaced, was told server not found: <server> as if the server had never existed. The aggregator now remembers a server whose entry it removed while its service is still alive: a call waits up to 10 seconds (or its own deadline) for the reconnect and is dispatched to the reconnected backend, or is answered server <server> is reconnecting: … retry the call shortly. A stopped or deleted server is still server not found. (#1531)