std::variant: Fixup .get() usage

This is just a refactor from the mapbox specific .get() interface to the
common std::variant ::get<>() interface.

Tested:
    Built and run through unit tests.

Change-Id: Ic0737f632e80c9dd5b73717ec33d31f245f107db
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/src/snmp_trap.cpp b/src/snmp_trap.cpp
index cc730b7..eb2efd3 100644
--- a/src/snmp_trap.cpp
+++ b/src/snmp_trap.cpp
@@ -33,11 +33,15 @@
         return;
     }
     auto& propMap = it->second;
-    auto errorID = propMap.at("Id").get<uint32_t>();
-    auto timestamp = propMap.at("Timestamp").get<uint64_t>();
-    auto sev = propMap.at("Severity").get<std::string>();
+    auto errorID =
+        sdbusplus::message::variant_ns::get<uint32_t>(propMap.at("Id"));
+    auto timestamp =
+        sdbusplus::message::variant_ns::get<uint64_t>(propMap.at("Timestamp"));
+    auto sev = sdbusplus::message::variant_ns::get<std::string>(
+        propMap.at("Severity"));
     auto isev = static_cast<uint8_t>(Entry::convertLevelFromString(sev));
-    auto message = propMap.at("Message").get<std::string>();
+    auto message =
+        sdbusplus::message::variant_ns::get<std::string>(propMap.at("Message"));
     try
     {
         sendTrap<OBMCErrorNotification>(errorID, timestamp, isev, message);