Yaml warning: loading can be potentially harmful

[tsjayram]

Describe the bug
The YAML loading can potentially be harmful, as seen in the run below. Applies to all scripts that use it.

/Users/jayram/Projects/mi-prometheus/miprometheus/utils/param_interface.py:283: YAMLLoadWarning: calling yaml.load() without Loader=... is deprecated, as the default Loader is unsafe. Please read https://msg.pyyaml.org/load for full details.
params_from_yaml = yaml.load(stream)

Desktop (please complete the following information):

• OS: both MacOS and Ubuntu Linux
• Python version 3.7
• PyTorch version 1.0

[tkornuta-ibm]

I have just checked the worker.py, which actually loads the config, and down there I use save_load:

            # Open file and get parameter dictionary.
            with open(config, 'r') as stream:
                param_dict = yaml.safe_load(stream)

I think the method in param_interface wasn't used... but fixed it anyway.