buffet: Use 15 second delay for StartDevice

Currenty, in order for StartDevice to work, the device must already be
online. This just gives us a bigger window for that to happen. (We
do retry 7 times but if the device is offline those retries happen very
fast.)

BUG=brillo:451
TEST=test_that <ip> buffet_Registration buffet_BasicDBusAPI

Change-Id: I9e51abf60999f674fab7071ff8bce3d61399fe49
Reviewed-on: https://chromium-review.googlesource.com/256370
Reviewed-by: Christopher Wiley <wiley@chromium.org>
Commit-Queue: Nathan Bullock <nathanbullock@google.com>
Tested-by: Nathan Bullock <nathanbullock@google.com>

buffet/manager.cc

diff --git a/buffet/manager.cc b/buffet/manager.cc
index 2e96fbc..c8c6974 100644
--- a/buffet/manager.cc
+++ b/buffet/manager.cc
@@ -79,7 +79,7 @@
   //             timeout as a configurable knob or allow local
   //             daemons to signal that their state is up to date so that
   //             we need not wait for them.
-  device_info_->ScheduleStartDevice(base::TimeDelta::FromSeconds(5));
+  device_info_->ScheduleStartDevice(base::TimeDelta::FromSeconds(15));
   dbus_adaptor_.RegisterWithDBusObject(&dbus_object_);
   dbus_object_.RegisterAsync(cb);
 }