add test case for duplicate keys in keyring (#870)

OpenKeychain/src/main/java/org/sufficientlysecure/keychain/pgp/CanonicalizedSecretKey.java

@@ -329,9 +329,9 @@ public class CanonicalizedSecretKey extends CanonicalizedPublicKey {
         return new UncachedSecretKey(mSecretKey);
     }
 
-    // HACK
-    public PGPSecretKey getSecretKey() {
-        return mSecretKey;
+    // HACK, for TESTING ONLY!!
+    PGPPrivateKey getPrivateKey () {
+        return mPrivateKey;
     }
 
 }

OpenKeychain/src/main/java/org/sufficientlysecure/keychain/pgp/PgpKeyOperation.java

@@ -1118,7 +1118,7 @@ public class PgpKeyOperation {
                 pKey, flags, expiry);
     }
 
-    private static PGPSignature generateSubkeyBindingSignature(
+    static PGPSignature generateSubkeyBindingSignature(
             PGPPublicKey masterPublicKey, PGPPrivateKey masterPrivateKey,
             PGPPrivateKey subPrivateKey, PGPPublicKey pKey, int flags, long expiry)
             throws IOException, PGPException, SignatureException {