[desktop] camera-app and unity8 freeze on startup while initializing gstreamer-0.10

[Andreas Pokorny]

qtmultimedia plugins like libgstcamerabin.so or libgstmediaplayer.so link against gstreamer-0.10:
ldd /usr/lib/x86_64-linux-gnu/qt5/plugins/mediaservice/libgstcamerabin.so
 [....]
 libgstinterfaces-0.10.so.0 => /usr/lib/x86_64-linux-gnu/libgstinterfaces-0.10.so.0 (0x00007fa8e4fdb000)
 libgstpbutils-0.10.so.0 => /usr/lib/x86_64-linux-gnu/libgstpbutils-0.10.so.0 (0x00007fa8e4db6000)
 libgstreamer-0.10.so.0 => /usr/lib/x86_64-linux-gnu/libgstreamer-0.10.so.0 (0x00007fa8e4acc000)

while UbuntuComponents links against gstreamer-1.0:

ldd /usr/lib/x86_64-linux-gnu/qt5/qml/Ubuntu/Components/libUbuntuComponents.so
 [...]
 libgstvideo-1.0.so.0 => /usr/lib/x86_64-linux-gnu/libgstvideo-1.0.so.0 (0x00007f65a3e9f000)

This seems to cause an initialization problem of gst-0.10:
(camera-app:6221): GLib-GObject-WARNING **: cannot register existing type 'GstFormat'

(camera-app:6221): GLib-CRITICAL **: g_once_init_leave: assertion 'result != 0' failed

(camera-app:6221): GLib-GObject-WARNING **: cannot retrieve class for invalid (unclassed) type '<invalid>'

(camera-app:6221): GLib-GObject-WARNING **: cannot register existing type 'GstQuery'

(camera-app:6221): GLib-CRITICAL **: g_once_init_leave: assertion 'result != 0' failed

(camera-app:6221): GLib-GObject-WARNING **: cannot retrieve class for invalid (unclassed) type '<invalid>'

(camera-app:6221): GLib-GObject-WARNING **: cannot register existing type 'GstObject'

(camera-app:6221): GLib-CRITICAL **: g_once_init_leave: assertion 'result != 0' failed

(camera-app:6221): GLib-GObject-WARNING **: cannot retrieve class for invalid (unclassed) type '<invalid>'

And that in turn makes the main thread of the application block indefinitely

ProblemType: Bug
DistroRelease: Ubuntu 14.10
Package: camera-app 3.0.0+14.10.20140829-0ubuntu1
ProcVersionSignature: Ubuntu 3.16.0-11.16-generic 3.16.1
Uname: Linux 3.16.0-11-generic x86_64
ApportVersion: 2.14.7-0ubuntu1
Architecture: amd64
CurrentDesktop: Unity
Date: Tue Sep 2 09:30:46 2014
InstallationDate: Installed on 2013-11-08 (297 days ago)
InstallationMedia: Ubuntu 14.04 LTS "Trusty Tahr" - Alpha amd64 (20131108)
SourcePackage: camera-app
SystemImageInfo: Error: [Errno 2] No such file or directory: 'system-image-cli'
UpgradeStatus: No upgrade log present (probably fresh install)

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.