OSC: Add waiters to share snapshot access create/delete

[Maari Tamm]

We are still missing the '--wait' option for share snapshot access create/delete commands.

All the OSC waiters use the wait_for_status[1][2] or wait_for_delete[3][4] options from osc_lib[5].
However, these require a way to retrieve one resource by its id, which we don't have for the share snapshot access rule. So, we'd need to figure out a way to implement this by retrieving the list of access rules and checking for the rule in question.

[1] https://github.com/openstack/osc-lib/blob/master/osc_lib/utils/__init__.py#L674
[2] https://github.com/openstack/python-manilaclient/blob/master/manilaclient/osc/v2/share.py#L266
[3] https://github.com/openstack/osc-lib/blob/master/osc_lib/utils/__init__.py#L623
[4] https://github.com/openstack/python-manilaclient/blob/master/manilaclient/osc/v2/share.py#L334
[5] https://github.com/openstack/osc-lib