osc/sm: Fix a bug that MPI_WIN_TEST does not update flag to 0

[kawashima-fj]

MPI_WIN_TEST must update the flag parameter to 0 when not all
origin processes called MPI_WIN_COMPLETE. But sm OSC doesn't.
If the caller initialize the flag argument to a non-0 value,
the caller will receive the non-0 flag value.

@hjelmn please review

I'll create PRs for v1.10 and v2.0.

[hjelmn]

👍

[kawashima-fj]

@hjelmn Do you have a plan to merge 903762e to v1.10 and v2.x branches?
Automatic merge on cherry-picking my fix fails because the commit is not merged into v1.10 and v2.x branches.

The bug I found exists in v1.10 and v2.x in another form. Code which set flag to 0 exists in a wrong position. The else block shoud correspond to if block of complete_count, not post_group.

Current v1.10/v2.x code:

    if (NULL != module->post_group) {
        int size = ompi_group_size(module->post_group);

        if (module->my_node_state->complete_count == size) {
            OBJ_RELEASE(module->post_group);
            module->post_group = NULL;
            *flag = 1;
        }
    } else {
        opal_atomic_mb();
        *flag = 0;
    }

[hjelmn]

Opening PRs now.