btl/ugni: honor enable_mpi_threads

Honor enable_mpi_threads setting to enable the ugni btl
async progress thread.  If the app doesn't request thread-multiple
the thread will not be created.

opal/mca/btl/ugni/btl_ugni.h

@@ -180,6 +180,10 @@ typedef struct mca_btl_ugni_component_t {
 
     /* Number of mailboxes to allocate in each block */
     unsigned int mbox_increment;
+
+    /* Indicate whether progress thread allowed */
+    bool progress_thread_allowed;
+
 } mca_btl_ugni_component_t;
 
 int mca_btl_ugni_module_init (mca_btl_ugni_module_t *ugni_module,

opal/mca/btl/ugni/btl_ugni_component.c

@@ -293,6 +293,10 @@ mca_btl_ugni_component_init (int *num_btl_modules,
         mca_btl_ugni_component.ugni_fma_limit = 65536;
     }
 
+    if (enable_mpi_threads) {
+        mca_btl_ugni_component.progress_thread_allowed = 1;
+    }
+
     /* Initialize ugni library and create communication domain */
     rc = opal_common_ugni_init();
     if (OPAL_SUCCESS != rc) {

opal/mca/btl/ugni/btl_ugni_module.c

@@ -116,7 +116,10 @@ mca_btl_ugni_module_init (mca_btl_ugni_module_t *ugni_module,
         return rc;
     }
 
-    if (getenv("HOWARDS_PROGESS") != NULL) howards_progress_var = 1;
+    if (mca_btl_ugni_component.progress_thread_allowed && (NULL != getenv("HOWARDS_PROGESS"))) {
+        howards_progress_var = 1;
+    }
+
     return OPAL_SUCCESS;
 }