verbs: Close async_fd only when it was previously created

Close async_fd only when it was previously created, otherwise the call
will fail and errno from previous failure (if exists) will be
overwritten.

Fixes: 1111cf9 ("verbs: Always allocate a verbs_context")
Signed-off-by: Yishai Hadas <yishaih@mellanox.com>

libibverbs/device.c

@@ -378,7 +378,8 @@ void verbs_uninit_context(struct verbs_context *context_ex)
 {
 	free(context_ex->priv);
 	close(context_ex->context.cmd_fd);
-	close(context_ex->context.async_fd);
+	if (context_ex->context.async_fd != -1)
+		close(context_ex->context.async_fd);
 	ibverbs_device_put(context_ex->context.device);
 }