IPA: Allow paging when fetching external groups
For some reason (I guess a mistake during refactoring..) the LDAP search
request that fetches the external groups does not enable the paging
control. This means that the number of external groups that SSSD can
fetch is limited to 2000.
Resolves: https://pagure.io/SSSD/sssd/issue/4058
Reviewed-by: Sumit Bose <sbose@redhat.com>