Podman usage improvements (#269)

* Remove pointless and confusing info where container images are pulled to
* Remove invalid CMD from podman run command

Author: dcermak

references/podman-usage.xml

@@ -53,10 +53,7 @@
       registry name. In that case, &podman; tries to pull the image from all
       registries configured in the
       <filename>/etc/containers/registries.conf</filename> file. The default
-      image tag is <literal>latest</literal>. The default location of pulled
-      images is
-      <filename>/var/lib/containers/storage/overlay-images/</filename>.
-    </para>
+      image tag is <literal>latest</literal>.
     <para>
       To view all possible options of the <command>podman pull</command>
       command, run:
@@ -114,7 +111,7 @@
         example that runs a container called <literal>sle15</literal> based on
         the latest <literal>sle15</literal> image follows:
       </para>
-<screen>&prompt.root;podman run registry.suse.com/suse/sle15:latest sle15</screen>
+<screen>&prompt.root;podman run registry.suse.com/suse/sle15:latest</screen>
       <para>
         Below is a list of frequently used options. For a complete list of
         available options, run the command: <command>podman run