btl openib: if ibv_open_device() returns NULL, it's not supported

When a libibverbs driver returns NULL for its context, it's the Open
MPI libibverbs fake driver.  Hence, this device is simply not
supported -- ignore it.

opal/mca/btl/openib/btl_openib_component.c

@@ -1581,7 +1581,7 @@ static int init_one_device(opal_list_t *btl_list, struct ibv_device* ib_dev)
     /* Open up the device */
     dev_context = ibv_open_device(ib_dev);
     if (NULL == dev_context) {
-        return OPAL_ERR_OUT_OF_RESOURCE;
+        return OPAL_ERR_NOT_SUPPORTED;
     }
 
     /* Find out if this device supports RC QPs */
@@ -2744,10 +2744,12 @@ btl_openib_component_init(int *num_btl_modules,
 
         found = true;
         ret = init_one_device(&btl_list, dev_sorted[i].ib_dev);
-        if (OPAL_SUCCESS != ret && OPAL_ERR_NOT_SUPPORTED != ret) {
+        if (OPAL_ERR_NOT_SUPPORTED == ret) {
+            ++num_devices_intentionally_ignored;
+            continue;
+        } else if (OPAL_SUCCESS != ret) {
             free(dev_sorted);
             goto no_btls;
-
         }
     }
     free(dev_sorted);