Solace Scaler: Enhancement to support a hostlist of Solace brokers

[dpochopsky]

This enhancement is to add support for Solace deployments with Disaster Recovery (DR) enabled. Solace DR introduces an additional Solace Broker and operates in an active standby mode, so the scaler needs to query two different brokers with different endpoints, verify connectivity status as well as determine which of the brokers are active, once that is deteremined, the scaler operates as it did before. The configuration file's 'solaceSempBaseURL' attribute will be updated to support a comma-separated list of Solace Broker endpoints.