Comment 1 for bug 354498

Leaving the domain fails to correctly restore various modified files, including /etc/apparmor.d/abstractions/nameservice.
It removes everything at the end of the original file:
  # likewise
  #include <abstractions/likewise>

  # mdnsd
  #include <abstractions/mdns>

  # kerberos
  #include <abstractions/kerberosclient>

  # TCP/UDP network access
  network inet stream,
  network inet6 stream,
  network inet dgram,
  network inet6 dgram,

This triggers various apparmor rules resulting in applicative breakage, of which DHCP failure in NetworkManager is probably just the visible tip of the iceberg.

Workaround is to run:
sudo cp /etc/apparmor.d/abstractions/nameservice.lwidentity.orig /etc/apparmor.d/abstractions/nameservice
Then reboot the machine