ipasam: implement PASSDB getgrnam call
    
    ipasam already implemented retrieval of groups for MS-SAMR calls.
    However, it did not have implementation of a group retrieval for the
    path of lookup_name() function in Samba. The lookup_name() is used in
    many places in smbd and winbindd.
    
    With this change it will be possible to resolve IPA groups in Windows UI
    (Security tab) and console (net localgroup ...). When Global Catalog
    service is enabled, it will be possible to search for those groups as
    well.
    
    In Active Directory, security groups can be domain, domain local, local
    and so on. In IPA, only domain groups exposed through ipasam because
    SID generation plugin only supports adding SIDs to POSIX groups and
    users. Thus, non-POSIX groups are not going to have SIDs associated and
    will not be visible in both UNIX and Windows environments.
    
    Group retrieval in Samba is implemented as a mapping between NT and
    POSIX groups. IPA doesn't have explicit mapping tables. Instead, any
    POSIX group in IPA that has a SID associated with it is considered a
    domain group for Samba.
    
    Finally, additional ACI is required to ensure attributes looked up by
    ipasam are always readable by the trust agents.
    
    Fixes: https://pagure.io/freeipa/issue/8660
    Signed-off-by: Alexander Bokovoy <abokovoy@redhat.com>
    Reviewed-By: Christian Heimes <cheimes@redhat.com>
    Reviewed-By: Rob Crittenden <rcritten@redhat.com>
    Reviewed-By: Christian Heimes <cheimes@redhat.com>
    Reviewed-By: Rob Crittenden <rcritten@redhat.com>