Merge branch 'ps/reftable-unit-test-nfs-workaround'

A unit test for reftable code tried to enumerate all files in a directory after reftable operations and expected to see nothing but the files it wanted to leave there, but was fooled by .nfs* cruft files left, which has been corrected. * ps/reftable-unit-test-nfs-workaround: reftable: fix tests being broken by NFS' delete-after-close semantics