servers/net: DHCPClient: Hard-code the message IDs.

Even though C++ should increment the enum for us, since these IDs
are set and used by things outside of this file, we should hard-code
the numbers.

No functional change (or if there is, it means there's a compiler bug
somewhere.)

src/servers/net/DHCPClient.cpp

@@ -85,14 +85,14 @@ enum message_option {
 
 enum message_type {
 	DHCP_NONE = 0,
-	DHCP_DISCOVER,
+	DHCP_DISCOVER = 1,
-	DHCP_OFFER,
+	DHCP_OFFER = 2,
-	DHCP_REQUEST,
+	DHCP_REQUEST = 3,
-	DHCP_DECLINE,
+	DHCP_DECLINE = 4,
-	DHCP_ACK,
+	DHCP_ACK = 5,
-	DHCP_NACK,
+	DHCP_NACK = 6,
-	DHCP_RELEASE,
+	DHCP_RELEASE = 7,
-	DHCP_INFORM
+	DHCP_INFORM = 8
 };
 
 struct dhcp_option_cookie {