Add missing retry

SignalServiceKit/src/Loki/API/DotNetAPI.swift

@@ -8,6 +8,7 @@ public class DotNetAPI : NSObject {
 
     // MARK: Settings
     private static let attachmentType = "network.loki"
+    private static let maxRetryCount: UInt = 4
     
     // MARK: Error
     @objc(LKDotNetAPIError)
@@ -123,7 +124,8 @@ public class DotNetAPI : NSObject {
         }
         let serverPublicKeyPromise = FileServerAPI.server.contains(host) ? Promise.value(FileServerAPI.fileServerPublicKey)
             : PublicChatAPI.getOpenGroupServerPublicKey(for: host)
-        return serverPublicKeyPromise.then2 { serverPublicKey in
+        return attempt(maxRetryCount: maxRetryCount, recoveringOn: SnodeAPI.workQueue) {
+            serverPublicKeyPromise.then2 { serverPublicKey in
                 return OnionRequestAPI.sendOnionRequest(request, to: host, using: serverPublicKey, isJSONRequired: false).map2 { json in
                     guard let body = json["body"] as? JSON, let data = body["data"] as? [UInt8] else {
                         print("[Loki] Couldn't parse attachment from: \(json).")
@@ -133,6 +135,7 @@ public class DotNetAPI : NSObject {
                 }
             }
         }
+    }
 
     @objc(uploadAttachment:withID:toServer:)
     public static func objc_uploadAttachment(_ attachment: TSAttachmentStream, with attachmentID: String, to server: String) -> AnyPromise {