Make <poolname> in "ceph osd tier --help" clearer (fix issue 8256).

Make &lt;poolname&gt; in "ceph osd tier --help" clearer.

The ceph osd tier --help info on the left always says &lt;poolname&gt;:

&quot;osd tier add &lt;poolname&gt; &lt;poolname&gt; force-nonempty}&quot;

Two &lt;poolname&gt; are the same. It is unclear which one to put &lt;tierpool&gt; according to descriptions the right:

&quot;add the tier &lt;tierpool&gt; to base pool &lt;pool&gt;&quot;

This patch modifies descriptions on the right to tell which &lt;poolname&gt;:

&quot;add the tier &lt;tierpool&gt; (the secondone) to base pool &lt;pool&gt; (the first one)&quot;

Fix: http://tracker.ceph.com/issues/8256

Signed-off-by: Yilong Zhao &lt;accelazh@gmail.com&gt;