tests: add testSubkeyAdd

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

@@ -101,6 +101,10 @@ public abstract class WrappedKeyRing extends KeyRing {
 
     abstract public IterableIterator<WrappedPublicKey> publicKeyIterator();
 
+    public byte[] getEncoded() throws IOException {
+        return getRing().getEncoded();
+    }
+
     public UncachedKeyRing getUncached() {
         return new UncachedKeyRing(getRing());
     }