Fix tests to pass when -preview suffix set in version (#121)

package.json

@@ -5,7 +5,7 @@
     "email": "azsdkteam@microsoft.com",
     "url": "https://github.com/Azure/ms-rest-azure-js"
   },
-  "version": "1.3.7",
+  "version": "1.3.8",
   "description": "Isomorphic Azure client runtime for Typescript/node.js/browser javascript client libraries generated using AutoRest",
   "tags": [
     "isomorphic",

test/azureServiceClientTests.ts

@@ -2523,7 +2523,7 @@ describe("AzureServiceClient", () => {
       delete expected.userAgent;
 
       assert.deepEqual(actual, expected);
-      assert(actualUserAgent!.match(/ms-rest-azure-js\/[\d\.]+ ms-rest-js\/[\d\.]+ .+/));
+      assert(actualUserAgent!.match(/ms-rest-azure-js\/[\d\.]+ ms-rest-js\/[\d\w\.-]+ .+/));
     }
 
     it("with undefined", () => {