Fix a hang in './test/hsa/ctrl ctrl_hsa_input_trace'

At the end of the test, the tracer tool is unloaded and the active
memory pools are flushed. In the flush callback, to get the activity
operation string, the RocpLoader instance is neeeded, and if the
RocpLoader is not already loaded, it attempts to dlopen the rocprofiler
library.

Calling dlopen from a global destructor hangs because the dynamic
loader lock is already owned (e.g. by dlclose).

To temporarily work around the issue, instanciate the RocpLoader when
the activities needing it are enabled.

Change-Id: I712c66d88c43694fe53a95d6a61d7b22abb75262

src/core/roctracer.cpp

@@ -939,6 +939,7 @@ static roctracer_status_t roctracer_enable_activity_fun(roctracer_domain_t domai
   switch (domain) {
     case ACTIVITY_DOMAIN_HSA_OPS: {
       if (op == HSA_OP_ID_COPY) {
+        roctracer::RocpLoader::Instance();
         roctracer::hsa_support::async_copy_callback_enabled = true;
         roctracer::hsa_support::async_copy_callback_memory_pool =
             reinterpret_cast<roctracer::MemoryPool*>(pool);
@@ -958,6 +959,7 @@ static roctracer_status_t roctracer_enable_activity_fun(roctracer_domain_t domai
     case ACTIVITY_DOMAIN_HSA_API:
       break;
     case ACTIVITY_DOMAIN_HSA_EVT:
+      roctracer::RocpLoader::Instance();
       break;
     case ACTIVITY_DOMAIN_HIP_OPS: {
       if (roctracer::HipLoader::Instance().Enabled() == false) break;