Fix the socket relay error handling and log level (#535)

- Downgrades a warning to the debug level in `BidirectionalRelay`
because the shutdown syscall isn't supported for certain socket types
- Rethrows an error if we can't start a socket relay

Sources/Containerization/UnixSocketRelayManager.swift

@@ -21,13 +21,13 @@ import Logging
 package actor UnixSocketRelayManager {
     private let vm: any VirtualMachineInstance
     private var relays: [String: UnixSocketRelay]
-    private let q: DispatchQueue
+    private let queue: DispatchQueue
     private let log: Logger?
 
     init(vm: any VirtualMachineInstance, log: Logger? = nil) {
         self.vm = vm
         self.relays = [:]
-        self.q = DispatchQueue(label: "com.apple.containerization.socket-relay")
+        self.queue = DispatchQueue(label: "com.apple.containerization.socket-relay")
         self.log = log
     }
 }
@@ -45,7 +45,7 @@ extension UnixSocketRelayManager {
             port: port,
             socket: socket,
             vm: vm,
-            queue: q,
+            queue: queue,
             log: log
         )
 
@@ -54,6 +54,7 @@ extension UnixSocketRelayManager {
             try await relay.start()
         } catch {
             relays.removeValue(forKey: socket.id)
+            throw error
         }
     }