move variant to std namespace

sdbusplus::message::variant_ns has been std for a while now. This moves
ipmid away from sdbusplus::message::variant_ns to directly use
std::variant.

Tested-by: built, compiles, and runs the same as before.

Change-Id: I8caa945f31c926c2721319f001b9d7f83fd3f1b7
Signed-off-by: Vernon Mauery <vernon.mauery@linux.intel.com>
diff --git a/host-cmd-manager.cpp b/host-cmd-manager.cpp
index 9efb787..f3aba7f 100644
--- a/host-cmd-manager.cpp
+++ b/host-cmd-manager.cpp
@@ -33,7 +33,6 @@
     sdbusplus::xyz::openbmc_project::Common::Error::InternalFailure;
 
 namespace sdbusRule = sdbusplus::bus::match::rules;
-namespace variant_ns = sdbusplus::message::variant_ns;
 
 Manager::Manager(sdbusplus::bus::bus& bus) :
     bus(bus), timer(std::bind(&Manager::hostTimeout, this)),
@@ -183,7 +182,7 @@
     }
 
     auto& requestedState =
-        variant_ns::get<std::string>(properties.at(HOST_TRANS_PROP));
+        std::get<std::string>(properties.at(HOST_TRANS_PROP));
 
     if (server::Host::convertTransitionFromString(requestedState) ==
         server::Host::Transition::On)