tests/functional: switch over to using self.scratch_file()

Replace any instances of

  os.path.join(self.workdir, ".../...")
  self.workdir + "/.../..."

with

  self.scratch_file("...", "...")

which is more compact and portable

Reviewed-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Message-ID: <20241217155953.3950506-15-berrange@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
45 files changed