samples: net: echo_service: mitigate sonarqube warning

This change mitigates a sonarqube warning about uninitialized variables.

"1st function call argument is an uninitialized value"

> Variables should be initialized before use c:S836

https://sonarcloud.io/project/issues?pullRequest=97152&\
open=AZnAZi0m7BgzESPFIGwe&id=zephyrproject-rtos_zephyr

Signed-off-by: Chris Friedt <[email protected]>

Author: cfriedt

samples/net/sockets/echo_service/src/main.c

@@ -172,7 +172,7 @@ static void tcp_accept_handler(struct net_socket_service_event *pev)
 	int client;
 	int sock = pev->event.fd;
 	char addr_str[INET6_ADDRSTRLEN];
-	struct sockaddr_in6 client_addr;
+	struct sockaddr_in6 client_addr = {};
 	socklen_t client_addr_len = sizeof(client_addr);
 
 	client = accept(sock, (struct sockaddr *)&client_addr, &client_addr_len);