sap_hana_install: Implement an SAP HANA installation check only feature

[berndfinger]

Fixes #844.

With this change, the role sap_hana_install can be used to perform an SAP HANA installation check without performing an installation.

[marcelmamula]

@berndfinger Name of this PR and Issue gives me hint that this detects already installed HANA on target, but that is not case based on code that debugs variables, not actual target contents.

I would suggest maybe renaming it to something clearer.

[berndfinger]

@berndfinger Name of this PR and Issue gives me hint that this detects already installed HANA on target, but that is not case based on code that debugs variables, not actual target contents.

The current version of the role can already check an existing HANA installation using one of these two methods, and it is doing this in the task named Perform an hdblcm installation check DIRECTLY AFTER a SAP HANA installation has been finished.

This PR, however, is only about adding the related tag to one more task so that the role does not fail when doing ONLY an installation check, in those cases where variables are used which have to be converted first.

[marcelmamula]

LGTM