sap_install_media_detect: Allow detection of SAPEXE only

[berndfinger]

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Solves issue #729.

[berndfinger]

I successfully tested with S/4HANA 2022 and with sap_install_media_detect_kernel_db unset (1) and set to absent (2). When unset (1) , the output showed correct content for the variables sap_swpm_kernel_dependent_path and sap_swpm_kernel_dependent_file_name. When set to absent (2), the two variables were empty.

[sean-freeman]

To confirm, this PR is to allow detection of "only SAPEXE" and "only SAPEXEDB" indepedently?

The current AND/OR logic seems to not match the above statement.

[berndfinger]

To confirm, this PR is to allow detection of "only SAPEXE" and "only SAPEXEDB" indepedently?

This PR is meant to support the detection of "only SAPEXE". By setting sap_install_media_detect_kernel_db to none, the role will no longer look for a SAPEXEDB file and will not report the two related output parameters for SAPEXEDB. If sap_install_media_detect_kernel is set to true and sap_install_media_detect_kernel_db is not set, the behavior is the same as before, meaning that the role will detect SAPEXE and SAPEXEDB.

If sap_install_media_detect_kernel_db is set and sap_install_media_detect_kernel is not set, the role will not display the output parameters for SAPEXE and SAPEXEDB. Also this case is probably not applicable, and it is out of scope for issue https://github.com/sap-linuxlab/community.sap_install/issues/729.