allow to disable shared HANA basepath and rework add_hosts code

[yeoldegrove]

needs SUSE/shaptools#70 and SUSE/salt-shaptools#88

Add feature to run hdblcm -action=add_hosts. This can be used to deploy scale-out scenarios on Azure/AWS/GCP without shared /hana/{data,log}.

• https://launchpad.support.sap.com/#/notes/2080991
• If we install a multi-host HANA DB with non-shared data and log storage, there is no other possibility than first installing the HANA primary master server and later adding additional nodes (after basepath_shared=no is set). No config option for the installer exists at the moment.
• see also https://documentation.suse.com/sbp/all/html/SLES-SAP-hana-scaleOut-PerfOpt-12-AWS/index.html#id-installation and https://docs.microsoft.com/en-us/azure/virtual-machines/workloads/sap/hana-vm-operations#installation-of-sap-hana-in-scale-out-configuration