Add VMSS priorty settings in example configuration files. By setting
priority to Low, Azure Spot instances can be used for the cluster,
thereby leading to potentially significant cost savings.
Update Azure VMSS documentation for the multiple VMSS scenario.
Update doc for running Muchos (for Azure clusters) on Ubuntu clients
to clarify Python package installation.
Add additional validations to ensure only Azure Spot capable VM SKUs
are used when the cluster is configured to use Azure Spot.
Low, Azure Spot instances can be used for the cluster, thereby leading to potentially significant cost savings.