device-monitor: list hidden providers before listing devices

The way it was implemented could make the list updated after the
list of device was filled with supposdely hidden devices
17 jobs for device_monitor in 60 minutes and 2 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Preparation
passed #280070
gst indent

00:00:47

passed #280069
manifest

00:00:38

 
  Build
passed #280071
build fedora x86_64

00:10:45

passed #280072
build nodebug fedora x86_64

00:10:29

 
  Test
passed #280073
check fedora

00:05:19

passed #280074
integration testsuites fedora

00:12:31

 
  Full Builds
passed #280076
build cerbero android universal

00:13:19

passed #280077
build cerbero cross win32

00:08:54

passed #280078
build cerbero cross win64

00:06:24

passed #280075
build cerbero fedora x86_64

00:05:07

 
  Full Tests
passed #280083
valgrind bad

00:13:34

passed #280080
valgrind base

00:09:45

passed #280079
valgrind core

00:10:11

passed #280084
valgrind ges

00:09:45

passed #280081
valgrind good

00:16:21

passed #280082
valgrind ugly

00:03:04

 
  Apps
passed #280085
android universal examples

00:06:15