winbind:varlink: Implement memberships by user

winbind:varlink: Implement memberships by user

$> userdbctl -s org.samba.winbind groups-of-user AFOREST+user1
Enabled services: org.samba.winbind
USER          GROUP
AFOREST+user1 AFOREST+domain users
AFOREST+user1 AFOREST+user1

2 memberships listed.

$> SYSTEMD_LOG_LEVEL=7 getent -sinitgroups:systemd initgroups "AFOREST+domain users"
varlink: Setting state idle-client
/run/systemd/userdb/org.samba.winbind: Sending message: {"method":"io.systemd.UserDatabase.GetMemberships","parameters":{"userName":"AFOREST+domain users","service":"org.samba.winbind"},"more":true}
/run/systemd/userdb/org.samba.winbind: Changing state idle-client → awaiting-reply-more
/run/systemd/userdb/org.samba.winbind: New incoming message: {"continues":true,"parameters":{"groupName":"AFOREST+domain users","userName":"AFOREST+domain users"}}
/run/systemd/userdb/org.samba.winbind: Changing state awaiting-reply-more → processing-reply
/run/systemd/userdb/org.samba.winbind: Changing state processing-reply → awaiting-reply-more
Failed to connect to /run/systemd/userdb/io.systemd.Multiplexer: No such file or directory
Unable to connect to /run/systemd/userdb/io.systemd.Multiplexer: No such file or directory
varlink: Setting state idle-client
/run/systemd/userdb/org.samba.winbind: Sending message: {"method":"io.systemd.UserDatabase.GetGroupRecord","parameters":{"groupName":"AFOREST+domain users","service":"org.samba.winbind"}}
/run/systemd/userdb/org.samba.winbind: Changing state idle-client → awaiting-reply
/run/systemd/userdb/org.samba.winbind: New incoming message: {"parameters":{"incomplete":false,"record":{"gid":20513,"groupName":"AFOREST+domain users","members":["AFOREST+administrator","AFOREST+user1","AFOREST+krbtgt"],"service":"org.samba.winbind"}}}
/run/systemd/userdb/org.samba.winbind: Changing state awaiting-reply → processing-reply
/run/systemd/userdb/org.samba.winbind: Changing state processing-reply → idle-client
/run/systemd/userdb/org.samba.winbind: New incoming message: {"parameters":{"groupName":"AFOREST+domain users","userName":"AFOREST+domain users"}}
/run/systemd/userdb/org.samba.winbind: Changing state awaiting-reply-more → processing-reply
/run/systemd/userdb/org.samba.winbind: Changing state processing-reply → idle-client
Failed to connect to /run/systemd/userdb/io.systemd.Multiplexer: No such file or directory
Unable to connect to /run/systemd/userdb/io.systemd.Multiplexer: No such file or directory
varlink: Setting state idle-client
/run/systemd/userdb/org.samba.winbind: Sending message: {"method":"io.systemd.UserDatabase.GetGroupRecord","parameters":{"groupName":"AFOREST+domain users","service":"org.samba.winbind"}}
/run/systemd/userdb/org.samba.winbind: Changing state idle-client → awaiting-reply
/run/systemd/userdb/org.samba.winbind: New incoming message: {"parameters":{"incomplete":false,"record":{"gid":20513,"groupName":"AFOREST+domain users","members":["AFOREST+administrator","AFOREST+user1","AFOREST+krbtgt"],"service":"org.samba.winbind"}}}
/run/systemd/userdb/org.samba.winbind: Changing state awaiting-reply → processing-reply
/run/systemd/userdb/org.samba.winbind: Changing state processing-reply → idle-client
AFOREST+domain users  20513 20513

Signed-off-by: Samuel Cabrero <scabrero@samba.org>
Reviewed-by: Andreas Schneider <asn@samba.org>