Fix nullptr failures for image upload

Several places that call *req.ioService were missing nullptr checks.
Add them, and fix the one case where it might not be filled in.

Tested:  With HTTP2 enabled, the following command succeeds.
```
curl -k https://192.168.7.2/redfish/v1/UpdateService/update -F 'UpdateParameters={"Targets":["/redfish/v1/Managers/bmc"]} ;type=application/json' --user "root:0penBmc" -F UpdateFile=@/home/ed/bmcweb/16mb.txt -v -H "Expect:"
```

Change-Id: I81e7944c22f5922d461bf5d231086c7468a16e62
Signed-off-by: Ed Tanous <ed@tanous.net>
diff --git a/redfish-core/lib/update_service.hpp b/redfish-core/lib/update_service.hpp
index 9ef8311..8617071 100644
--- a/redfish-core/lib/update_service.hpp
+++ b/redfish-core/lib/update_service.hpp
@@ -405,6 +405,12 @@
         return;
     }
 
+    if (req.ioService == nullptr)
+    {
+        messages::internalError(asyncResp->res);
+        return;
+    }
+
     fwAvailableTimer =
         std::make_unique<boost::asio::steady_timer>(*req.ioService);