Delay needed at end of add_to_group()

[bdemchak]

If I create a group (using create_group) and then add all nodes and edges to the group (using add_to_group), the group should contain all nodes and edges and the id of the group, per Scooter.

It does this, but the id of the group seems to be added in a second phase that occurs after CyREST has already returned. So, calling get_group_info() immediately after this shows that the group ID is missing. A delay is needed before this test can return the proper result.

For this test, I use galFiltered, and it's possible that the delay should be added in other group functions ... more testing is needed.