Bug#763628: It is possible to override such behavior.

[Oleksandr Gavenko]

I trapped to inability to flush built-in connman DNS cache:

  https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=805797

Solution to run connman with:

  $ cat /etc/default/connman
  DAEMON_OPTS='--nodnsproxy'

See CONNMAN(8).

-- 
Best regards!