Protect mosq->ssl_ctx against double initialisation.

lib/net_mosq.c

@@ -458,6 +458,7 @@ static int net__init_ssl_ctx(struct mosquitto *mosq)
 	}
 
 	if(mosq->tls_cafile || mosq->tls_capath || mosq->tls_psk){
+		if(!mosq->ssl_ctx){
 #if OPENSSL_VERSION_NUMBER < 0x10100000L
 			mosq->ssl_ctx = SSL_CTX_new(SSLv23_client_method());
 #else
@@ -470,6 +471,7 @@ static int net__init_ssl_ctx(struct mosquitto *mosq)
 				net__print_ssl_error(mosq);
 				return MOSQ_ERR_TLS;
 			}
+		}
 
 		if(!mosq->tls_version){
 			SSL_CTX_set_options(mosq->ssl_ctx, SSL_OP_NO_SSLv3);