scripts: add rsync to test dependencies
scripts: add rsync to test dependencies

In order to be able to use 'rsync -ni' as a replacement for 'diff -r'
(needed for the renameat2 test cases, and to improve the method of
comparing directory trees) we need to have rsync installed on all ZFS
test platforms.

Signed-off-by: Aleksa Sarai <b305c9b0212d6145eea67bbffd24e29cb79c759c@cyphar.com>

zfsonlinux/zfs-buildbot,zfsonlinux/zfs-buildbot