Workaround an apparent problem with Mrack conversion of HW requirements

It seems that when only an actual filtering element is the filter, mrack
renders an element without attributes. It might be a mrack bug, or us
not understanding mrack API, but a quick workaround to unblock tmt is
possible. If it's a mrack bug, the proper fix may come later; if it's us
not giving mrack the correct structure, well, this patch fixes that. We
should be covered in both directions.

Fixes #3442

Author: happz

tmt/steps/provision/mrack.py

@@ -784,8 +784,15 @@ def _translate_tmt_hw(self, hw: tmt.hardware.Hardware) -> dict[str, Any]:
 
             logger.debug('Transformed hardware', tmt.utils.dict_to_yaml(transformed.to_mrack()))
 
+            # Mrack does not handle well situation when the filter
+            # consists of just a single filtering element, e.g. just
+            # `hostname`. In that case, the element is converted into
+            # XML element incorrectly. Therefore wrapping our filter
+            # with `<and/>` group, even if it has just a single child,
+            # it works around the problem.
+            # See https://github.com/teemtee/tmt/issues/3442
             return {
-                'hostRequires': transformed.to_mrack()
+                'hostRequires': MrackHWAndGroup(children=[transformed]).to_mrack()
                 }
 
         def create_host_requirement(self, host: CreateJobParameters) -> dict[str, Any]: