Add mtu to dhcp

templates/etc/dhcp/dhcpd.conf.j2

@@ -12,7 +12,10 @@ subnet {{ dhcp.subnet }} netmask {{ dhcp.netmask }} {
     range {{ dhcp.range.start }} {{ dhcp.range.end }};
     option routers {{ dhcp.router }};
     option domain-name-servers {{ dhcp.name_servers }};
-{% if dhcp.search %}
+{% if dhcp.mtu is defined %}
+    option interface-mtu {{ dhcp.mtu }};
+{% endif %}
+{% if dhcp.search is defined %}
     option domain-name "{{ dhcp.search }}";
 {% endif %}
 }