Add mqtt.require_time, use in Azure and GCP

Azure (when using SAS token) and GCP require valid time to sign tokens.
It doesn't make sense to even bother connecting if time is not set.

CL: mqtt: Add mqtt.require_time, use in Azure and GCP

PUBLISHED_FROM=e09615bf127c39aa3fec11226230530d61cd0258

src/mgos_azure.c

@@ -139,6 +139,7 @@ bool mgos_azure_init(void) {
     mcfg.client_id = mcfg.user = mcfg.pass = NULL;
     mcfg.ssl_cert = mcfg.ssl_key = NULL;
     mgos_mqtt_set_connect_fn(mgos_azure_mqtt_connect, s_ctx);
+    mcfg.require_time = true;
     auth_method = "SAS";
   } else if (mgos_sys_config_get_azure_host_name() != NULL &&
              mgos_sys_config_get_azure_device_id() != NULL &&