build: implement a framework for starting test servers during tests

Test servers are implemented by docker containers and run real servers
for rclone to test against.

backend/sftp/sftp_test.go

@@ -8,13 +8,24 @@ import (
 	"testing"
 
 	"github.com/rclone/rclone/backend/sftp"
+	"github.com/rclone/rclone/fstest"
 	"github.com/rclone/rclone/fstest/fstests"
 )
 
 // TestIntegration runs integration tests against the remote
 func TestIntegration(t *testing.T) {
 	fstests.Run(t, &fstests.Opt{
-		RemoteName: "TestSftp:",
+		RemoteName: "TestSFTPOpenssh:",
+		NilObject:  (*sftp.Object)(nil),
+	})
+}
+
+func TestIntegration2(t *testing.T) {
+	if *fstest.RemoteName != "" {
+		t.Skip("skipping as -remote is set")
+	}
+	fstests.Run(t, &fstests.Opt{
+		RemoteName: "TestSFTPRclone:",
 		NilObject:  (*sftp.Object)(nil),
 	})
 }