Merge pull request #175 from msabramo/osutil.AuthOptions_append_tokens_to_provider

osutil.AuthOptions appends /tokens to provider
diff --git a/osutil/auth.go b/osutil/auth.go
index 409846c..a411b63 100644
--- a/osutil/auth.go
+++ b/osutil/auth.go
@@ -4,6 +4,7 @@
 	"fmt"
 	"github.com/rackspace/gophercloud"
 	"os"
+	"strings"
 )
 
 var (
@@ -55,5 +56,9 @@
 		TenantName: tenantName,
 	}
 
+	if !strings.HasSuffix(provider, "/tokens") {
+		provider += "/tokens"
+	}
+
 	return provider, ao, nil
 }