update.py should not adopt parameters from zeronet.conf

### Step 1: Please describe your environment

* ZeroNet version: r4485
* Operating system: Raspbian
* Python 3.7.3

### Step 2: Describe the problem:

Hello, it does not seem handy when update.py adopt parameters from zeronet.conf:

cd /home/me/zeronet/
python3 zeronet.py --version

> - Starting ZeroNet...
> - Libsecpk256k1 loaded: CompiledLib in 0.094s
> ZeroNet 0.7.1 r4485

python3 update.py

> usage: update.py [-h] [--verbose] [--debug] [--silent] [--debug_socket]
> ...
> update.py: error: unrecognized arguments: --autodownload_bigfile_size_limit 200 --optional_limit 62 --ui_password mypassword