TBR: veyron/security: Fix test build broken by
https://veyron-review.googlesource.com/#/c/6376/

Change-Id: I41c28be03fa4fdd05c3b2e24ce010e4a2099f824
diff --git a/security/blessingroots_test.go b/security/blessingroots_test.go
index 899651c..f129d9e 100644
--- a/security/blessingroots_test.go
+++ b/security/blessingroots_test.go
@@ -15,7 +15,7 @@
 	var tester rootsTester
 	var err error
 	for idx := range tester {
-		if tester[idx], _, err = newKey(); err != nil {
+		if tester[idx], _, err = NewPrincipalKey(); err != nil {
 			panic(err)
 		}
 	}