Check if FCV is initialized before performing feature flag check in setClusterParameter and getClusterParameter

Currently, both getClusterParameter and setClusterParameter on 6.0 assert that featureFlagClusterWideConfig are enabled before running. featureFlagClusterWideConfig is enabled by default if FCV >= 6.0. In addition to checking that the feature flag is enabled, the commands should first check that FCV has been initialized so that the feature flag check is possible and makes sense.