Return a copy when explicitly asked for one (fixes a test).

components/net/sf/briar/crypto/ErasableKeyImpl.java

@@ -31,7 +31,7 @@ class ErasableKeyImpl implements ErasableKey {
 	}
 
 	public ErasableKey copy() {
-		return new ErasableKeyImpl(getEncoded(), algorithm);
+		return new ErasableKeyImpl(key.clone(), algorithm);
 	}
 
 	public synchronized void erase() {