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/http/http2_connection.hpp b/http/http2_connection.hpp
index d5f4481..3e0c394 100644
--- a/http/http2_connection.hpp
+++ b/http/http2_connection.hpp
@@ -246,6 +246,8 @@
             }
         }
         crow::Request& thisReq = it->second.req;
+        thisReq.ioService = static_cast<decltype(thisReq.ioService)>(
+            &adaptor.get_executor().context());
         BMCWEB_LOG_DEBUG("Handling {} \"{}\"", logPtr(&thisReq),
                          thisReq.url().encoded_path());