Activation: Support to update multiple PSUs

Queue the update on multiple PSUs, and do the update one-by-one.

Tested: Write unit test cases and verify the cases pass.
        On witherspoon, verify the dummy update services are run on all
        PSUs.

Signed-off-by: Lei YU <mine260309@gmail.com>
Change-Id: Icfe0f6e74623e54840df8d731d852d53d6071768
diff --git a/test/mocked_utils.hpp b/test/mocked_utils.hpp
index 7afe07c..85f5ffc 100644
--- a/test/mocked_utils.hpp
+++ b/test/mocked_utils.hpp
@@ -33,7 +33,7 @@
                            const char* propertyName));
 };
 
-const UtilsInterface& getUtils()
+inline const UtilsInterface& getUtils()
 {
     static MockedUtils utils;
     return utils;