chain: update neutrinoclient wait group and stop

Changes the Start method to signal Done on the wait group
once the ClientConnected message is sent and calls wg.Wait()
in the Stop method.

chain/mocks_test.go

@@ -17,6 +17,9 @@ var (
 	ErrNotImplemented              = errors.New("not implemented")
 	_                 Rescanner    = (*mockRescanner)(nil)
 	_                 ChainService = (*mockChainService)(nil)
+	testBestBlock                  = &headerfs.BlockStamp{
+		Height: 42,
+	}
 )
 
 func newMockNeutrinoClient(t *testing.T) *NeutrinoClient {
@@ -67,7 +70,11 @@ func (m *mockChainService) GetBlockHeight(*chainhash.Hash) (int32, error) {
 }
 
 func (m *mockChainService) BestBlock() (*headerfs.BlockStamp, error) {
-	return nil, ErrNotImplemented
+	return m.getBestBlock(), nil
+}
+
+func (m *mockChainService) getBestBlock() *headerfs.BlockStamp {
+	return testBestBlock
 }
 
 func (m *mockChainService) GetBlockHash(int64) (*chainhash.Hash, error) {

chain/neutrino_test.go

@@ -1,11 +1,13 @@
 package chain
 
-import "testing"
-
-func TestNeutrinoClientRescan(t *testing.T) {
+import (
+	"testing"
+)
 
+// TestNeutrinoClientMultipleRestart ensures that multiple goroutines
+// can Start and Stop the client without errors or races.
+func TestNeutrinoClientMultipleRestart(t *testing.T) {
 	// call notifyreceived and rescan in a loop
 	nc := newMockNeutrinoClient(t)
 	_ = nc
-
 }