API connection error while running as service

[forcerk]

I'm running mopidy behind a company proxy and looking forward to run mopidy as a service.
So I've added a /etc/default/mopidy file with the following input:

http_proxy=http://Username:Password@ProxyServer:80
https_proxy=http://Username:Password@ProxyServer:80

Added the following lines to the /etc/init.d/mopidy:
[ -f /etc/default/mopidy ] && . /etc/default/mopidy

Here is my mopidy config file. (~/.config/mopidy/mopidy.conf is the same like /etc/mopidy/mopidy.conf)
# For further information about options in this file see:
#   http://docs.mopidy.com/
#
# The initial commented out values reflect the defaults as of:
#   Mopidy 2.1.0
#   Mopidy-File 2.1.0
#   Mopidy-HTTP 2.1.0
#   Mopidy-Local 2.1.0
#   Mopidy-M3U 2.1.0
#   Mopidy-MPD 2.1.0
#   Mopidy-SoftwareMixer 2.1.0
#   Mopidy-Stream 2.1.0
#
# Available options and defaults might have changed since then,
# run `mopidy config` to see the current effective config and
# `mopidy --version` to check the current version.

[core]
cache_dir = /var/cache/mopidy
config_dir = /etc/mopidy
data_dir = /var/lib/mopidy
#max_tracklist_length = 10000
#restore_state = false

[logging]
color = true
console_format = %(levelname)-8s %(message)s
debug_format = %(levelname)-8s %(asctime)s [%(process)d:%(threadName)s] %(name)s\n  %(message)s
debug_file = mopidy.log
config_file = /etc/mopidy/logging.conf

[audio]
mixer = software
mixer_volume = 30
#output = autoaudiosink
#buffer_time =

[proxy]
scheme = http
hostname = proxyserverhostname
port = 80
username = User
password = Password

[mpd]
#enabled = true
#hostname = 127.0.0.1
#port = 6600
#password =
#max_connections = 20
#connection_timeout = 60
#zeroconf = Mopidy MPD server on $hostname
#command_blacklist =
#  listall
#  listallinfo
#default_playlist_scheme = m3u

[http]
enabled = true
hostname = 10.138.175.132
port = 6680
#static_dir =
#zeroconf = Mopidy HTTP server on $hostname

[stream]
enabled = true
protocols =
  http
  https
  mms
  rtmp
  rtmps
  rtsp
#metadata_blacklist =
#timeout = 5000

[m3u]
#enabled = true
#base_dir =
#default_encoding = latin-1
#default_extension = .m3u8
#playlists_dir =

[softwaremixer]
#enabled = true

[file]
#enabled = true
#media_dirs =
#  $XDG_MUSIC_DIR|Music
#  ~/|Home
#excluded_file_extensions =
#  .jpg
#  .jpeg
#show_dotfiles = false
#follow_symlinks = false
#metadata_timeout = 1000

[local]
#enabled = true
#library = json
media_dir = /tmp
#scan_timeout = 1000
#scan_flush_threshold = 100
#scan_follow_symlinks = false
#excluded_file_extensions =
#  .directory
#  .html
#  .jpeg
#  .jpg
#  .log
#  .nfo
#  .png
#  .txt

[musicbox_webclient]
enabled = true
musicbox = true
websocket_host =
websocket_port =
on_track_click = PLAY_NOW

[dirble]
api_key = 64somerandom738387cf9fwc
countries = US,GB,NO
timeout = 5000

[websettings]
enabled = true
musicbox = true
config_file = /etc/mopidy/mopidy.conf

Like this I'm able to listen to SomaFM for example. But if I browse for dirble stations the log is showing the following Error:
WARNING [1832:DirbleBackend-8] mopidy_dirble.client: Fetching Dirble data failed: HTTPConnectionPool(host='api.dirble.com', port=80): Max retries exceeded with url: /v2/categories/tree?token=642c6a258dbe4eea1f39ce4c8b (Caused by NewConnectionError('<requests.packages.urllib3.connection.HTTPConnection object at 0xaf599950>: Failed to establish a new connection: [Errno 101] Network is unreachable',))

If I'm starting mopidy from the shell like (root@mopidybox:/# mopidy) I can browse dirble and listen to the radio.
Is this a permission thing with the mopidy user which is used while running it as a service?