Fix Invalid Auxiliary Token issue (#444)

Change to semicolon to comma.
Fix the failed test case

Author: msJinLei

src/ResourceManager.Test/AzureRMCmdletAuthenticationUnitTests.cs

@@ -105,7 +105,7 @@ public void TestGetAuxHeaderByTenantIds()
                 var h = header.First();
                 Assert.Equal("x-ms-authorization-auxiliary", h.Key);
                 Assert.Single(h.Value);
-                var tokens = h.Value.First().Split(';');
+                var tokens = h.Value.First().Split(AzureRMCmdlet.AUX_TOKEN_APPEND_CHAR);
                 var regex = new Regex(@"Bearer ([0-9a-zA-Z]+)");
                 for (int i = 0; i < tenants.Count; ++i)
                 {

src/ResourceManager/Version2016_09_01/AzureRMCmdlet.cs

@@ -49,7 +49,7 @@ public abstract class AzureRMCmdlet : AzurePSCmdlet, IDynamicParameters
         public const int MAX_NUMBER_OF_TOKENS_ALLOWED_IN_AUX_HEADER = 3;
         public const string AUX_HEADER_NAME = "x-ms-authorization-auxiliary";
         public const string AUX_TOKEN_PREFIX = "Bearer";
-        public const string AUX_TOKEN_APPEND_CHAR = ";";
+        public const string AUX_TOKEN_APPEND_CHAR = ",";
         public const string WriteDebugKey = "WriteDebug";
         public const string WriteVerboseKey = "WriteVerbose";
         public const string WriteWarningKey = "WriteWarning";