Fix bsc#1173007: Clarify vgdisplay

In SLE15, we don't use Cluster VG anymore, but
instead of Shared VG.

The vgdisplay doesn't print this information, but
it can be retrieved by the "vgs" command.

Apply suggestions from code review. Many thanks
to Tanja and Liam!

Co-authored-by: Liam Proven <lproven@users.noreply.github.com>
Co-authored-by: Tanja Roth <taroth21@users.noreply.github.com>
(cherry picked from commit bb76cb7)

xml/ha_cluster_lvm.xml

@@ -558,8 +558,6 @@ Login to [iface: default, target: iqn.2010-03.de.&wsI;:san1, portal: &wwwip;,326
       Metadata Sequence No  1
       VG Access             read/write
       VG Status             resizable
-      Clustered             yes
-      Shared                no
       MAX LV                0
       Cur LV                0
       Open LV               0
@@ -573,6 +571,20 @@ Login to [iface: default, target: iqn.2010-03.de.&wsI;:san1, portal: &wwwip;,326
       Free  PE / Size       254 / 1016,00 MB
       VG UUID               UCyWw8-2jqV-enuT-KH4d-NXQI-JhH3-J24anD</screen>
     </step>
+    <step>
+     <para>
+      Check the shared state of the volume group with the command <command>vgs</command>:
+     </para>
+     <screen>&prompt.root;<command>vgs</command>
+  VG       #PV #LV #SN Attr   VSize     VFree  
+  vgshared   1   1   0 wz--ns 1016.00m  1016.00m</screen>
+     <para>
+      The <literal>Attr</literal> column shows the volume attributes. In this example,
+      the volume group is writable (<literal>w</literal>),
+      resizeable (<literal>z</literal>), the allocation policy is normal (<literal>n</literal>),
+      and it is a shared resource (<literal>s</literal>).
+      See the man page of <command>vgs</command> for details.</para>
+    </step>
    </procedure>
    <para>
     After you have created the volumes and started your resources you should have new device