Without net-misc/bridge-utils:

  time="2015-12-06T22:16:29.188000836Z" level=info msg="[graphdriver] using prior storage driver \"btrfs\""
  time="2015-12-06T22:16:29.188262957Z" level=info msg="API listen on /var/run/docker.sock"
  time="2015-12-06T22:16:29.193934168Z" level=info msg="Firewalld running: false"
  time="2015-12-06T22:16:29.256724387Z" level=fatal msg="Error starting daemon: Error initializing network controller: Error creating default \"bridge\" network: failed to parse pool request for address space \"LocalDefault\" pool \"\" subpool \"\": could not find an available predefined network"

With net-misc/bridge-utils:

  time="2015-12-06T22:20:37.535025525Z" level=info msg="[graphdriver] using prior storage driver \"btrfs\""
  time="2015-12-06T22:20:37.536608128Z" level=info msg="API listen on /var/run/docker.sock"
  time="2015-12-06T22:20:37.537824624Z" level=info msg="Firewalld running: false"
  time="2015-12-06T22:20:37.573149055Z" level=info msg="Default bridge (docker0) is assigned with an IP address 172.17.42.1/16. Daemon option --bip can be used to set a preferred IP address"
  time="2015-12-06T22:20:37.627085610Z" level=warning msg="Your kernel does not support kernel memory limit."
  time="2015-12-06T22:20:37.627274265Z" level=warning msg="mountpoint for blkio not found"
  time="2015-12-06T22:20:37.628085667Z" level=info msg="Loading containers: start."
  time="2015-12-06T22:20:37.628258966Z" level=info msg="Loading containers: done."
  time="2015-12-06T22:20:37.628278066Z" level=info msg="Daemon has completed initialization"
  time="2015-12-06T22:20:37.628296985Z" level=info msg="Docker daemon" commit=a34a1d5 execdriver=native-0.2 graphdriver=btrfs version=1.9.1