Update U-boot env variables

- If the new priority is the lowest then set the uboot to point
  to that particular version
- Otherwise reset the Uboot environment variable to find the version
  with the lowest priority and then set that in uboot.

Resolves openbmc/openbmc#2512

Change-Id: Id27e78a85662e0ff2e941515bb467a43c6076d96
Signed-off-by: Saqib Khan <khansa@us.ibm.com>
diff --git a/activation.hpp b/activation.hpp
index cf4b5c2..6c303db 100644
--- a/activation.hpp
+++ b/activation.hpp
@@ -266,6 +266,13 @@
         void unsubscribeFromSystemdSignals();
 
         /**
+         * @brief Updates the U-Boot variables to point to this activation's
+         *        versionId, so that the systems boots from this version on
+         *        the next reboot.
+         */
+        void updateUbootEnvVars();
+
+        /**
          * @brief delete the d-bus object.
          */
         void delete_() override;