Make sure context is set before getting stream

Context was not set before getting stream, leading to invalid context in
multi threaded application.

Author: Hugh Delaney

source/adapters/cuda/enqueue.cpp

@@ -625,6 +625,7 @@ UR_APIEXPORT ur_result_t UR_APICALL urEnqueueMemBufferReadRect(
 
   ur_lock MemoryMigrationLock{hBuffer->MemoryMigrationMutex};
   auto Device = hQueue->getDevice();
+  ScopedContext Active(Device);
   CUstream Stream = hQueue->getNextTransferStream();
 
   try {
@@ -644,8 +645,6 @@ UR_APIEXPORT ur_result_t UR_APICALL urEnqueueMemBufferReadRect(
                                        &hBuffer->LastEventWritingToMemObj));
     }
 
-    ScopedContext Active(Device);
-
     UR_CHECK_ERROR(enqueueEventsWait(hQueue, Stream, numEventsInWaitList,
                                      phEventWaitList));
 
@@ -1640,6 +1639,7 @@ UR_APIEXPORT ur_result_t UR_APICALL urEnqueueMemBufferRead(
   std::unique_ptr<ur_event_handle_t_> RetImplEvent{nullptr};
   ur_lock MemoryMigrationLock{hBuffer->MemoryMigrationMutex};
   auto Device = hQueue->getDevice();
+  ScopedContext Active(Device);
   CUstream Stream = hQueue->getNextTransferStream();
 
   try {
@@ -1659,8 +1659,6 @@ UR_APIEXPORT ur_result_t UR_APICALL urEnqueueMemBufferRead(
                                        &hBuffer->LastEventWritingToMemObj));
     }
 
-    ScopedContext Active(Device);
-
     UR_CHECK_ERROR(enqueueEventsWait(hQueue, Stream, numEventsInWaitList,
                                      phEventWaitList));