tgz: extract using tar-stream directly

we used have a fork of tar-fs. using tar-stream directly gives us
more control

src/storage/gcs.js

@@ -73,29 +73,20 @@ async function getAvailableSize(apiConfig) {
     return Number.POSITIVE_INFINITY;
 }
 
-function upload(apiConfig, backupFilePath, sourceStream, callback) {
+async function upload(apiConfig, backupFilePath) {
     assert.strictEqual(typeof apiConfig, 'object');
     assert.strictEqual(typeof backupFilePath, 'string');
-    assert.strictEqual(typeof sourceStream, 'object');
-    assert.strictEqual(typeof callback, 'function');
 
     debug(`Uploading to ${backupFilePath}`);
 
-    function done(error) {
-        if (error) {
-            debug(`upload: [${backupFilePath}] gcp upload error. %o`, error);
-            return callback(new BoxError(BoxError.EXTERNAL_ERROR, `Error uploading ${backupFilePath}. Message: ${error.message} HTTP Code: ${error.code}`));
-        }
+    const uploadStream = getBucket(apiConfig)
+        .file(backupFilePath)
+        .createWriteStream({ resumable: false });
 
-        callback(null);
-    }
-
-    const uploadStream = getBucket(apiConfig).file(backupFilePath)
-        .createWriteStream({resumable: false})
-        .on('finish', done)
-        .on('error', done);
-
-    sourceStream.pipe(uploadStream);
+    return {
+        uploadStream,
+        async finish() {}
+    };
 }
 
 async function exists(apiConfig, backupFilePath) {