Merge branch 'bugfix/fix_tcp_transprot_ssl_read_blocked' into 'master'

fix(tcp_transport): fix SSL read blocked when the connecttion is closed

See merge request sdk/ESP8266_RTOS_SDK!983

components/tcp_transport/transport_ssl.c

@@ -129,6 +129,7 @@ static int ssl_read(esp_transport_handle_t t, char *buffer, int len, int timeout
     ret = esp_tls_conn_read(ssl->tls, (unsigned char *)buffer, len);
     if (ret <= 0) {
         ESP_LOGE(TAG, "esp_tls_conn_read error, errno=%s", strerror(errno));
+        return -1;
     }
     return ret;
 }