IFP: add org.freedesktop.sssd.infopipe.Users.User
Example calls:
dbus-send --print-reply --system --dest=org.freedesktop.sssd.infopipe /org/freedesktop/sssd/infopipe/Users/LDAP_2ePB/10001 org.freedesktop.DBus.Properties.Get string:org.freedesktop.sssd.infopipe.Users.User string:name
method return sender=:1.159 -> dest=:1.165 reply_serial=2
variant string "user-1"
Resolves:
https://fedorahosted.org/sssd/ticket/2150
Reviewed-by: Jakub Hrozek <jhrozek@redhat.com>