ostree.TestReferenceSignaturePath: fix a compiler warning in a test
ostree.TestReferenceSignaturePath: fix a compiler warning in a test

Fix a compile warning in a test.

Signed-off-by: Nalin Dahyabhai <f562fcb2a0b898bf0be1afc867ea92325d8f825f@redhat.com>

containers/image,containers/image