docs + fix test

Signed-off-by: Nikita Tarasov <nikita@mygento.ru>

docs/storage-drivers/swift.md

@@ -298,6 +298,16 @@ An implementation of the `storagedriver.StorageDriver` interface that uses [Open
     </p>
     </td>
 </tr>
+<tr>
+    <td>
+    <code>authversion</code>
+    </td>
+    <td>
+    <p>
+    Optionally, specify the OpenStack Auth's version,for example <code>3</code>. The driver use 0 (autodetect) by default.
+    </p>
+    </td>
+</tr>
 <tr>
     <td>
     <code>chunksize</code>

registry/storage/driver/swift/swift_test.go

@@ -53,7 +53,7 @@ func init() {
 	trustID = os.Getenv("SWIFT_TRUST_ID")
 	container = os.Getenv("SWIFT_CONTAINER_NAME")
 	region = os.Getenv("SWIFT_REGION_NAME")
-	AuthVersion = strconv.Atoi(os.Getenv("SWIFT_AUTH_VERSION"))
+	AuthVersion, _ = strconv.Atoi(os.Getenv("SWIFT_AUTH_VERSION"))
 	insecureSkipVerify, _ = strconv.ParseBool(os.Getenv("SWIFT_INSECURESKIPVERIFY"))
 	secretKey = os.Getenv("SWIFT_SECRET_KEY")
 	accessKey = os.Getenv("SWIFT_ACCESS_KEY")