Added clientruntime test framework DLL to RS Backup test project.

Author: Samuel Anudeep

src/ResourceManager/RecoveryServices.Backup/Commands.RecoveryServices.Backup.Test/packages.config

@@ -7,6 +7,7 @@
   <package id="Microsoft.IdentityModel.Clients.ActiveDirectory" version="2.28.3" targetFramework="net45" />
   <package id="Microsoft.Rest.ClientRuntime" version="2.3.3" targetFramework="net45" />
   <package id="Microsoft.Rest.ClientRuntime.Azure" version="3.3.3" targetFramework="net45" />
+  <package id="Microsoft.Rest.ClientRuntime.Azure.TestFramework" version="1.3.6-preview" targetFramework="net45" />
   <package id="Microsoft.WindowsAzure.Management" version="4.1.1" targetFramework="net45" />
   <package id="Newtonsoft.Json" version="6.0.8" targetFramework="net45" />
   <package id="xunit" version="2.1.0" targetFramework="net45" />