Fix std::variant usage

We need to conform to the std::variant interface instead of the mapbox
specific one.

Change-Id: I3edbcb2682ddfebfcbca6e75284b11f2e18cfd11
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/utils.hpp b/utils.hpp
index efcd50c..08b10e8 100644
--- a/utils.hpp
+++ b/utils.hpp
@@ -70,7 +70,7 @@
         sdbusplus::message::variant<T> value{};
         auto reply = bus.call(method);
         reply.read(value);
-        return value.template get<T>();
+        return sdbusplus::message::variant_ns::get<T>(value);
     }
     catch (const sdbusplus::exception::SdBusError& ex)
     {