sap_hana_install: Allow the role to only perform an installation check

[berndfinger]

By adding the tag sap_hana_install_check_installation to the task Rename some variables used by hdblcm configfile, we can quickly enable the role sap_hana_install to only check an existing installation.

Users would have to call the role with role parameter sap_hana_install_check_installation and also include the tag with this name. Note: Without the tag, the role would perform the installation check in addition to the installation attempt.

The role could of course also be redesigned to only perform an installation check without using the tag - for example using a new role parameter sap_hana_install_check_installation_only