network: Configure DNS servers

EL systems use DNS servers from interface configs so support it.

roles/network/templates/ifcfg-eth.j2

@@ -21,6 +21,12 @@ NETMASK="{{ item.netmask }}"
 {%   if item.gateway is defined %}
 GATEWAY="{{ item.gateway }}"
 {%   endif %}
+{%   if item.nameservers is defined %}
+PEERDNS=no
+{%     for i in range(item.nameservers|length) %}
+DNS{{ i+1 }}={{ item.nameservers[i] }}
+{%     endfor %}
+{%   endif %}
 {% elif proto == 'none' %}
 BOOTPROTO=none
 {% endif %}