rocr: Don't assert in hsa_shut_down when no agents (#1115)

* rocr: Don't assert in hsa_shut_down when no agents

Instead, print error message and return an error. Prior to
this patch, the assertion would occur when hsa_shut_down() is
called more than once.

* rocr: Reorder Unload  ASAN clean-up on shut down

projects/rocr-runtime/runtime/hsa-runtime/core/runtime/runtime.cpp

@@ -2256,12 +2256,12 @@ void Runtime::Unload() {
   mapped_handle_map_.clear();
   memory_handle_map_.clear();
 
-  DestroyAgents();
-
   CloseTools();
 
   AMD::Unload();
 
+  DestroyAgents();
+
   DestroyDrivers();
 
   thunkLoader_->DestroyThunkInstance();