BUG/MINOR: server/cli: Fix locking in function processing "set server" command

The commit c7b391aed ("BUG/MEDIUM: server/cli: Fix ABBA deadlock when fqdn
is set from the CLI") introduced 2 bugs. The first one is a typo on the
server's lock label (s/SERVER_UNLOCK/SERVER_LOCK/). The second one is about
the server's lock itself. It must be acquired to execute the "agent-send"
subcommand.

The patch above is marked to be backported as far as 1.8. Thus, this one
must also backported as far 1.8.

BUG/MINOR: server/cli: Don't forget to lock server on agent-send subcommand

(cherry picked from commit 0ba54bb40102787ce875c5d15cb0fb4193f178ec)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
(cherry picked from commit 88fca377546267d24ab23cb7f7d2e0eef9d71ee6)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
diff --git a/src/server.c b/src/server.c
index 5507d20..3569fd1 100644
--- a/src/server.c
+++ b/src/server.c
@@ -4484,12 +4484,14 @@
 		HA_SPIN_UNLOCK(SERVER_LOCK, &sv->lock);
 	}
 	else if (strcmp(args[3], "agent-send") == 0) {
+		HA_SPIN_LOCK(SERVER_LOCK, &sv->lock);
 		if (!(sv->agent.state & CHK_ST_ENABLED))
 			cli_err(appctx, "agent checks are not enabled on this server.\n");
 		else {
 			if (!set_srv_agent_send(sv, args[4]))
 				cli_err(appctx, "cannot allocate memory for new string.\n");
 		}
+		HA_SPIN_UNLOCK(SERVER_LOCK, &sv->lock);
 	}
 	else if (strcmp(args[3], "check-port") == 0) {
 		int i = 0;
@@ -4548,7 +4550,7 @@
 			sv->flags &= ~SRV_F_NO_RESOLUTION;
 		}
 		warning = update_server_fqdn(sv, args[4], "stats socket command", 1);
-		HA_SPIN_UNLOCK(SERVER_UNLOCK, &sv->lock);
+		HA_SPIN_UNLOCK(SERVER_LOCK, &sv->lock);
 		HA_SPIN_UNLOCK(DNS_LOCK, &sv->resolvers->lock);
 		if (warning)
 			cli_msg(appctx, LOG_WARNING, warning);