docs: Move 'echo' command description into the generic commands section

Virsh's echo command looks not having any relations with domains and its
description should go into the generic commands section instead of the
domain commands section (current).

tools/virsh.pod

@@ -373,6 +373,13 @@ guest CPU definition is the <cpu> element and its contents from domain XML
 definition. For more information on guest CPU definition see:
 L<http://libvirt.org/formatdomain.html#elementsCPU>
 
+=item B<echo> [I<--shell>] [I<--xml>] [I<arg>...]
+
+Echo back each I<arg>, separated by space.  If I<--shell> is
+specified, then the output will be single-quoted where needed, so that
+it is suitable for reuse in a shell context.  If I<--xml> is
+specified, then the output will be escaped for use in XML.
+
 =back
 
 =head1 DOMAIN COMMANDS
@@ -632,13 +639,6 @@ Using I<--security-info> will also include security sensitive information
 in the XML dump. I<--update-cpu> updates domain CPU requirements according to
 host CPU.
 
-=item B<echo> [I<--shell>] [I<--xml>] [I<arg>...]
-
-Echo back each I<arg>, separated by space.  If I<--shell> is
-specified, then the output will be single-quoted where needed, so that
-it is suitable for reuse in a shell context.  If I<--xml> is
-specified, then the output will be escaped for use in XML.
-
 =item B<edit> I<domain-id>
 
 Edit the XML configuration file for a domain, which will affect the