[FAB-13167] IdemixBridgeTest Robustification

This change-set updates the tests to always
correctly invalidate a credential in a bad path test.

Change-Id: I3a0eda33bf1158d7a1cf8a3ddd7dc4c4af5548dd
Signed-off-by: Angelo De Caro <adc@zurich.ibm.com>

Author: adecaro

bccsp/idemix/bridge/bridge_test.go

@@ -849,7 +849,13 @@ var _ = Describe("Idemix Bridge", func() {
 			})
 
 			It("invalid credential", func() {
-				credential[4] = 0
+				// Invalidate credential by changing it in one position
+				if credential[4] == 0 {
+					credential[4] = 1
+				} else {
+					credential[4] = 0
+				}
+
 				// Verify Credential
 				valid, err := CredentialVerifier.Verify(
 					UserKey,