std::variant: Fix forgotten conversion

Change-Id: Ie802ac340ebc0fde965bd84e18d2af9391136626
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/activation.cpp b/activation.cpp
index 4a54fbb..7f3537f 100644
--- a/activation.cpp
+++ b/activation.cpp
@@ -363,7 +363,7 @@
     sdbusplus::message::variant<bool> fieldMode;
     reply.read(fieldMode);
 
-    return (fieldMode.get<bool>());
+    return sdbusplus::message::variant_ns::get<bool>(fieldMode);
 }
 
 std::string Activation::getService(sdbusplus::bus::bus& bus,