roles/dhcpcd: Always send FQDN

Though the default for the `fqdn` value is listed as `both` in
*dhcpcd.conf(5)*, the current behavior of `dhcpcd` suggests that it may
actually be `none`. Without explicitly setting `fqdn both`, the value of
the kernel node name is sent as-is in the *hostname* option (12). If the
node name is set to the FQDN, then dynamic DNS gets broken, since the
DHCP server always appends its domain name to the provided hostname.
Setting `fqdn both` causes `dhcpcd` to send the FQDN in the *FQDN*
option (81), which the DHCP server interprets correctly.

roles/dhcpcd/templates/dhcpcd.conf.j2

@@ -28,6 +28,9 @@ hostname
 #hostname
 {% endif %}
 
+# Always send FQDN
+fqdn both
+
 # Use the hardware address of the interface for the Client ID.
 {% if dhcpcd_use_clientid|bool %}
 clientid