Fix flaky hardlinks test
The test was added in
dc34990, it turns out that it's flaky. It failed
once on the Debian build infra, cf. [1].
The problem is that the command `rsync -aH '$fromdir/sym' '$todir'`
updates the mod time of `$todir`, so there might be a diff between the
output of `rsync_ls_lR $fromdir` and `rsync_ls_lR $todir`, if ever rsync
runs 1 second (or more) after the directories were created.
To clarify: it's easy to make the test fails 100% of the times with this
change:
```
makepath "$fromdir/sym" "$todir"
+sleep 5
checkit "$RSYNC -aH '$fromdir/sym' '$todir'" "$fromdir" "$todir"
```
With the fix proposed here, we don't use `checkit` anymore, instead we
just run the rsync command, then a simple `diff` to compare the two
directories. This is exactly what the other `-H` test just above does.
In case there's some doubts, `diff` fails if `sym` is missing:
```
$ mkdir -p foo/sym bar
$ diff foo bar || echo KO!
Only in foo: sym
KO!
```
I tested that, after this commit, the test still catches the `-H`
regression in rsync 3.4.0.
Fixes: https://github.com/RsyncProject/rsync/issues/735
[1]: https://buildd.debian.org/status/fetch.php?pkg=rsync&arch=ppc64el&ver=3.4.1%2Bds1-1&stamp=
1741147156&raw=0