settings/d-bus: fix boolean return value of "LoadConnections"

The boolean value is intended to indicate success. It would indicated
failure due to a bug.

Fixes: 297d4985 ('core/dbus: rework D-Bus implementation to use lower layer GDBusConnection API'):
(cherry picked from commit 22e830f0)
10 jobs for nm-1-18 in 37 minutes and 43 seconds (queued for 1 second)
Status Job ID Name Coverage
  Test
passed #292212
checkpatch

00:00:58

passed #292219
t_debian:9

00:14:19

passed #292221
t_debian:sid

00:16:06

manual #292220
allowed to fail manual
t_debian:testing
passed #292213
t_fedora:28

00:29:09

passed #292214
t_fedora:29

00:37:42

passed #292215
t_fedora:30

00:27:54

manual #292216
allowed to fail manual
t_fedora:rawhide
passed #292217
t_ubuntu:16.04

00:16:18

passed #292218
t_ubuntu:18.04

00:16:22