Description of problem:

Attempting to get extraAttributes via SSSD's ifp fails.

Version-Release number of selected component (if applicable):

sssd-dbus-2.0.0-4.fc29.x86_64

How reproducible:

Deterministic.

Steps to Reproduce:
1. Install and configure FreeIPA server, for example via
   ipa-server-install -r EXAMPLE.TEST -n example.test -p Secret123 -a Secret123
2. Attempt to get extraAttributes for user admin:
   dbus-send --print-reply --system --dest=org.freedesktop.sssd.infopipe /org/freedesktop/sssd/infopipe/Users/example_2etest/$( id -u admin ) org.freedesktop.DBus.Properties.Get string:"org.freedesktop.sssd.infopipe.Users.User" string:"extraAttributes"

Actual results:

Error org.freedesktop.DBus.Error.UnknownProperty: Unknown property

Expected results:

method return time=1545051067.561377 sender=:1.96 -> destination=:1.115 serial=15 reply_serial=2
   variant       array [
      ]

Additional info:

This is regression against sssd-dbus-1.16.3-2.fc28.x86_64 and older versions.

This is breaking Ipsilon. It was found when testing https://pagure.io/webauthinfra on Fedora 29: testing https://travis-ci.org/adelton/webauthinfra/builds/466857916