Trivial fix: in dhcp-host the name is optional

Although in IPv4 one must pick either mac or name, either
can be omitted.  Similarly, for IPv6, the name
can be optionally omitted.
Signed-off-by: NGene Czarcinski <gene@czarc.net>
Signed-off-by: NLaine Stump <laine@laine.org>

docs/schemas/network.rng

@@ -278,10 +278,15 @@
                 </zeroOrMore>
                 <zeroOrMore>
                   <element name="host">
-                    <optional>
+                    <choice>
+                      <group>
                         <attribute name="mac"><ref name="uniMacAddr"/></attribute>
+                        <optional>
+                          <attribute name="name"><text/></attribute>
                         </optional>
+                      </group>
                       <attribute name="name"><text/></attribute>
+                    </choice>
                     <attribute name="ip"><ref name="ipAddr"/></attribute>
                   </element>
                 </zeroOrMore>