Use more specific includes

We shouldn't be including all of asio, just the parts we need.

Change-Id: I15f5ffa40311644df98fcb9164cac529a423d232
Signed-off-by: Ed Tanous <edtanous@google.com>
diff --git a/example/get-all-properties.cpp b/example/get-all-properties.cpp
index 8a5c680..428b322 100644
--- a/example/get-all-properties.cpp
+++ b/example/get-all-properties.cpp
@@ -1,4 +1,5 @@
-#include <boost/asio.hpp>
+#include <boost/asio/io_context.hpp>
+#include <boost/asio/signal_set.hpp>
 #include <sdbusplus/asio/connection.hpp>
 #include <sdbusplus/asio/object_server.hpp>
 #include <sdbusplus/asio/property.hpp>