remove usage of sdbusplus::message::variant

sdbusplus has had its alias of std::variant in place for long
enough. This changes all ipmid references to use std::variant
directly instead of the sdbusplus alias.

Tested-by: building and running ipmid

Change-Id: Id5b4136d4589aa598815edd3ef4202e64a7698e2
Signed-off-by: Vernon Mauery <vernon.mauery@linux.intel.com>
diff --git a/selutility.cpp b/selutility.cpp
index 0d71a47..615ad81 100644
--- a/selutility.cpp
+++ b/selutility.cpp
@@ -138,7 +138,7 @@
     using AssociationList =
         std::vector<std::tuple<std::string, std::string, std::string>>;
 
-    sdbusplus::message::variant<AssociationList> list;
+    std::variant<AssociationList> list;
     reply.read(list);
 
     auto& assocs = std::get<AssociationList>(list);
@@ -200,7 +200,7 @@
         elog<InternalFailure>();
     }
 
-    sdbusplus::message::variant<uint64_t> timeStamp;
+    std::variant<uint64_t> timeStamp;
     reply.read(timeStamp);
 
     std::chrono::milliseconds chronoTimeStamp(std::get<uint64_t>(timeStamp));