syncrepl code fails to store cookie after REFRESH phase completes and it switches to PERSIST

[quanah]

If you found a bug in python-ldap, or would request a new feature,
this is the place to let us know.

Please describe the issue and your environment here.

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Issue description:

When using the syncrepl code in python-ldap, if you have an idle system after the REFRESH phase completes and it switches to persist mode, and then shut down the sync client with no changes having happened with the LDAP server, the sync cookie is never saved (syncrepl_set_cookie is not called). If the process is started on a system with active changes, syncrepl_set_cookie is correctly called after every new change once it has switched to PERSIST phase

Steps to reproduce:

Run a syncrepl client against an ldap environment using refreshAndPersist mode, where no changes occur after persist mode has occurred.

Operating system:

linux

Python version:

3.10.12

python-ldap version:

3.4.3

[quanah]

Found that during the refreshDelete phase, no cookie ends up being stored.