MINOR: server: cli: Add server FQDNs to server-state file and stats socket.

This patch adds a new stats socket command to modify server
FQDNs at run time.
Its syntax:
  set server <backend>/<server> fqdn <FQDN>
This patch also adds FQDNs to server state file at the end
of each line for backward compatibility ("-" if not present).
diff --git a/include/types/server.h b/include/types/server.h
index 8d68dcb..83b1e80 100644
--- a/include/types/server.h
+++ b/include/types/server.h
@@ -82,6 +82,7 @@
 	SRV_ADMF_IDRAIN    = 0x10,        /* the server has inherited the drain status from a tracked server */
 	SRV_ADMF_DRAIN     = 0x18,        /* mask to check if any drain flag is present */
 	SRV_ADMF_RMAINT    = 0x20,        /* the server is down because of an IP address resolution failure */
+	SRV_ADMF_HMAINT    = 0x40,        /* the server FQDN has been set from socket stats */
 };
 
 /* options for servers' "init-addr" parameter
@@ -103,7 +104,26 @@
 #define SRV_STATE_FILE_VERSION 1
 #define SRV_STATE_FILE_VERSION_MIN 1
 #define SRV_STATE_FILE_VERSION_MAX 1
-#define SRV_STATE_FILE_FIELD_NAMES "be_id be_name srv_id srv_name srv_addr srv_op_state srv_admin_state srv_uweight srv_iweight srv_time_since_last_change srv_check_status srv_check_result srv_check_health srv_check_state srv_agent_state bk_f_forced_id srv_f_forced_id"
+#define SRV_STATE_FILE_FIELD_NAMES \
+    "be_id "                      \
+    "be_name "                    \
+    "srv_id "                     \
+    "srv_name "                   \
+    "srv_addr "                   \
+    "srv_op_state "               \
+    "srv_admin_state "            \
+    "srv_uweight "                \
+    "srv_iweight "                \
+    "srv_time_since_last_change " \
+    "srv_check_status "           \
+    "srv_check_result "           \
+    "srv_check_health "           \
+    "srv_check_state "            \
+    "srv_agent_state "            \
+    "bk_f_forced_id "             \
+    "srv_f_forced_id "            \
+    "srv_fqdn"
+
 #define SRV_STATE_FILE_MAX_FIELDS 18
 #define SRV_STATE_FILE_NB_FIELDS_VERSION_1 18
 #define SRV_STATE_LINE_MAXLEN 512