Default activeProfiles to ['default']

[daecabhir]

CloudConfigOptionsSchema currently requires that the developer specify at least one profile to activate, when there may be no explicit profiles defined in the configuration set (e.g., if development, test and production are served by completely different configuration servers). The Joi schema definition for this could be set up to default activeProfiles to ['default'] if not supplied, rather than having SpringCloudConfig#load throw an error.