unionfs-fuse: fix build warning

WARNING: QA Issue: /usr/sbin/mount.unionfs_unionfs-fuse contained in package unionfs-fuse requires /bin/bash, but no providers found in its RDEPENDS [file-rdeps]

Signed-off-by: Armin Kuster <akuster808@gmail.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>