[release-v2.0] loader: Only create mix client if mixing enabled.

wallet.Config is created in three separate places (create new wallet,
open existing wallet, watch only wallet). DisableMixing was only being
set correctly in one of those (watch only). As a result, a MixClient
would always be created regardless of config set by the user.

Backport of 7552d0b.

Author: jholdstock

internal/loader/loader.go

@@ -277,6 +277,7 @@ func (l *Loader) CreateNewWallet(ctx context.Context, pubPassphrase, privPassphr
 		WatchLast:               l.watchLast,
 		AccountGapLimit:         l.accountGapLimit,
 		DisableCoinTypeUpgrades: l.disableCoinTypeUpgrades,
+		DisableMixing:           l.disableMixing,
 		StakePoolColdExtKey:     so.StakePoolColdExtKey,
 		ManualTickets:           l.manualTickets,
 		AllowHighFees:           l.allowHighFees,
@@ -338,6 +339,7 @@ func (l *Loader) OpenExistingWallet(ctx context.Context, pubPassphrase []byte) (
 		WatchLast:               l.watchLast,
 		AccountGapLimit:         l.accountGapLimit,
 		DisableCoinTypeUpgrades: l.disableCoinTypeUpgrades,
+		DisableMixing:           l.disableMixing,
 		StakePoolColdExtKey:     so.StakePoolColdExtKey,
 		ManualTickets:           l.manualTickets,
 		AllowHighFees:           l.allowHighFees,

wallet/chainntfns.go

@@ -277,7 +277,9 @@ func (w *Wallet) ChainSwitch(ctx context.Context, forest *SidechainForest, chain
 	forest.PruneChain(chain)
 	forest.Prune(int32(chain[len(chain)-1].Header.Height), w.chainParams)
 
-	w.mixClient.ExpireMessages(chain[len(chain)-1].Header.Height)
+	if w.mixing {
+		w.mixClient.ExpireMessages(chain[len(chain)-1].Header.Height)
+	}
 
 	w.NtfnServer.notifyMainChainTipChanged(chainTipChanges)
 	w.NtfnServer.sendAttachedBlockNotification(ctx)