Following up on my previously posted config,
I found the following message in /var/vcap/sys/log/cloud_controller_ng/cloud_controller_ng.log (The error log was empty... ):

Problem is that I don't understand ow "APPDOMAIN" violates the rules in the error message

{"timestamp":1467040322.8311825,"message":"Encountered error: Error for shared domain name APPDOMAIN: name can contain multiple subdomains, each having only alphanumeric characters and hyphens of up to 63 characters, see RFC 1035.\n/var/vcap/packages/cloud_controller_ng/cloud_controller_ng/vendor/bundle/ruby/2.3.0/gems/sequel-4.29.0/lib/sequel/model/base.rb:1543:in `save'\n/var/vcap/packages/cloud_controller_ng/cloud_controller_ng/app/models/runtime/shared_domain.rb:35:in `block in find_or_create'\n/var/vcap/packages/cloud_controller_ng/cloud_controller_ng/vendor/bundle/ruby/2.3.0/gems/sequel-4.29.0/lib/sequel/database/transactions.rb:134:in `_transaction'\n/var/vcap/packages/cloud_controller_ng/cloud_controller_ng/vendor/bundle/ruby/2.3.0/gems/sequel-4.29.0/lib/sequel/database/transactions.rb:108:in `block in transaction'\n/var/vcap/packages/cloud_controller_ng/cloud_controller_ng/vendor/bundle/ruby/2.3.0/gems/sequel-4.29.0/lib/sequel/database/connecting.rb:249:in `block in synchron
ize'\n/var/vcap/packages/cloud_controller_ng/cloud_controller_ng/vendor/bundle/ruby/2.3.0/gems/sequel-4.29.0/lib/sequel/connection_pool/threaded.rb:103:in `hold'\n/var/vcap/packages/cloud_controller_ng/cloud_controller_ng/vendor/bundle/ruby/2.3.0/gems/sequel-4.29.0/lib/sequel/database/connecting.rb:249:in `synchronize'\n/var/vcap/packages/cloud_controller_ng/cloud_controller_ng/vendor/bundle/ruby/2.3.0/gems/sequel-4.29.0/lib/sequel/database/transactions.rb:97:in `transaction'\n/var/vcap/packages/cloud_controller_ng/cloud_controller_ng/app/models/runtime/shared_domain.rb:27:in `find_or_create'\n/var/vcap/data/packages/cloud_controller_ng/f87cb49aa2cd87792cb9c2211a79e1542502be4d.1-08d000452ce2b287c00720587f20dc62976a73b6/cloud_controller_ng/lib/cloud_controller/seeds.rb:57:in `block in create_seed_domains'\n/var/vcap/data/packages/cloud_controller_ng/f87cb49aa2cd87792cb9c2211a79e1542502be4d.1-08d000452ce2b287c00720587f20dc62976a73b6/cloud_controller_ng/lib/cloud_controller/seeds.rb:56
:in `
each'\n/var/vcap/data/packages/cloud_controller_ng/f87cb49aa2cd87792cb9c2211a79e1542502be4d.1-08d000452ce2b287c00720587f20dc62976a73b6/cloud_controller_ng/lib/cloud_controller/seeds.rb:56:in `create_seed_domains'\n/var/vcap/data/packages/cloud_controller_ng/f87cb49aa2cd87792cb9c2211a79e1542502be4d.1-08d000452ce2b287c00720587f20dc62976a73b6/cloud_controller_ng/lib/cloud_controller/seeds.rb:9:in `write_seed_data'\n/var/vcap/data/packages/cloud_controller_ng/f87cb49aa2cd87792cb9c2211a79e1542502be4d.1-08d000452ce2b287c00720587f20dc62976a73b6/cloud_controller_ng/lib/cloud_controller/runner.rb:88:in `block in run!'\n/var/vcap/packages/cloud_controller_ng/cloud_controller_ng/vendor/bundle/ruby/2.3.0/gems/eventmachine-1.0.9.1/lib/eventmachine.rb:193:in `run_machine'\n/var/vcap/packages/cloud_controller_ng/cloud_controller_ng/vendor/bundle/ruby/2.3.0/gems/eventmachine-1.0.9.1/lib/eventmachine.rb:193:in `run'\n/var/vcap/data/packages/cloud_controller_ng/f87cb49aa2cd87792cb9c2211a79e1542502be4d
.1-08d000452ce2b287c00720587f20dc62976a73b6/cloud_controller_ng/lib/cloud_controller/runner.rb:82:in `run!'\n/var/vcap/packages/cloud_controller_ng/cloud_controller_ng/bin/cloud_controller:8:in `<main>'","log_level":"error","source":"cc.runner","data":{},"thread_id":47219093041420,"fiber_id":47219133477120,"process_id":27911,"file":"/var/vcap/data/packages/cloud_controller_ng/f87cb49aa2cd87792cb9c2211a79e1542502be4d.1-08d000452ce2b287c00720587f20dc62976a73b6/cloud_controller_ng/lib/cloud_controller/runner.rb","lineno":102,"method":"rescue in block in run!"}