relay: don't reconnect when we don't have to

We are reconnecting multiple times for two separate reasons:

1. On a cancellation "error" which does not warrant a reconnect

2. In our reconnection backoff it doesn't check If we are already
   connecting or connected. We check this so we don't reconnect multiple
   times.

This fixes many reconnection issues and makes Damus feel wayyy snappier.

Signed-off-by: William Casarin <jb55@jb55.com>

damus/Nostr/RelayConnection.swift

@@ -141,6 +141,10 @@ final class RelayConnection: ObservableObject {
                 // ignore socket not connected?
                 return
             }
+            if nserr.domain == NSURLErrorDomain && nserr.code == -999 {
+                // these aren't real error, it just means task was cancelled
+                return
+            }
             DispatchQueue.main.async {
                 self.isConnected = false
                 self.isConnecting = false
@@ -157,14 +161,21 @@ final class RelayConnection: ObservableObject {
     }
     
     func reconnect_with_backoff() {
-        self.backoff *= 1.5
+        self.backoff *= 2.0
         self.reconnect_in(after: self.backoff)
     }
     
     func reconnect() {
         guard !isConnecting && !isDisabled else {
+            self.log?.add("Cancelling reconnect, already connecting")
             return  // we're already trying to connect or we're disabled
         }
+
+        guard !self.isConnected else {
+            self.log?.add("Cancelling reconnect, already connected")
+            return
+        }
+
         disconnect()
         connect()
         log?.add("Reconnecting...")