Put remote boot UUID in ServerStatistics and RemoteMessage

This makes it so we can see when a remote reboots easily, and gives us a
stepping stone to putting it in the log file header.

RemoteMessage then goes to the logger, so we are ready to teach the
logger how to detect and handle reboots.

Change-Id: I943de46094b60535c92a677b430d6828933b820d
diff --git a/aos/events/shm_event_loop.cc b/aos/events/shm_event_loop.cc
index fed5f4c..2a0d332 100644
--- a/aos/events/shm_event_loop.cc
+++ b/aos/events/shm_event_loop.cc
@@ -222,7 +222,7 @@
 }  // namespace
 
 ShmEventLoop::ShmEventLoop(const Configuration *configuration)
-    : EventLoop(configuration),
+    : EventLoop(configuration, UUID::BootUUID()),
       shm_base_(FLAGS_shm_base),
       name_(FLAGS_application_name),
       node_(MaybeMyNode(configuration)) {