Drop no longer needed is_selinux_supported() (#3191)

Guest `has_selinux` fact should be used instead, now when we have guest
facts.

tmt/steps/provision/podman.py

@@ -366,10 +366,13 @@ def push(
         if not self.is_ready:
             return
 
-        self.debug("Update selinux context of the run workdir.", level=3)
+        assert self.parent.plan.my_run is not None  # narrow type
         assert self.parent.plan.workdir is not None  # narrow type
+
         # Relabel workdir to container_file_t if SELinux supported
-        if tmt.utils.is_selinux_supported():
+        self.debug("Update selinux context of the run workdir.", level=3)
+
+        if self.parent.plan.my_run.runner.facts.has_selinux:
             self._run_guest_command(Command(
                 "chcon", "--recursive", "--type=container_file_t", self.parent.plan.workdir
                 ), shell=False, silent=True)

tmt/utils/__init__.py

@@ -5832,17 +5832,6 @@ def field(
         )
 
 
-@functools.cache
-def is_selinux_supported() -> bool:
-    """
-    Returns ``true`` if SELinux filesystem is supported by the kernel, ``false`` otherwise.
-
-    For detection ``/proc/filesystems`` is used, see ``man 5 filesystems`` for details.
-    """
-    with open('/proc/filesystems') as file:
-        return any('selinuxfs' in line for line in file)
-
-
 def locate_key_origin(node: fmf.Tree, key: str) -> Optional[fmf.Tree]:
     """
     Find an fmf node where the given key is defined.