Convert variant usage to std interface

This is just a refactoring to use the c++17 std::variant interfaces
instead of the mapbox::variant specific ones. We should be able to use
mapbox::variant and std::variant interchangeably now.

Tested:
    Built against sdbusplus with mapbox::variant and sbusplus using
    std::variant. Both variant compile and test out.

Change-Id: I6fbaad3d12dd34968db6a10f3d74a65e07d0f0cc
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/utils.cpp b/utils.cpp
index 06c26e8..f6a840a 100644
--- a/utils.cpp
+++ b/utils.cpp
@@ -7,6 +7,7 @@
 #include <algorithm>
 #include <phosphor-logging/elog-errors.hpp>
 #include <phosphor-logging/log.hpp>
+#include <sdbusplus/message/types.hpp>
 #include <xyz/openbmc_project/Common/error.hpp>
 
 namespace ipmi
@@ -14,6 +15,7 @@
 
 using namespace phosphor::logging;
 using namespace sdbusplus::xyz::openbmc_project::Common::Error;
+namespace variant_ns = sdbusplus::message::variant_ns;
 
 namespace network
 {
@@ -116,7 +118,7 @@
         objectInfo = std::make_pair(object.first, object.second.begin()->first);
 
         // if LinkLocalIP found look for Non-LinkLocalIP
-        if (ipmi::network::isLinkLocalIP(variant.get<std::string>()))
+        if (ipmi::network::isLinkLocalIP(variant_ns::get<std::string>(variant)))
         {
             continue;
         }