bug(docker): bind docker bridge to a specific IP

Docker chooses an unused IP range for its network bridge, but more
than once we have seen this conflict with the Vagrant bridge, which
is presumably created after the Docker bridge. This commit uses
a specific CIDR for the Docker bridge, which does not conflict with the
Vagrant IP.

fixes #702
Merge pull request #717 from opdemand/carmstrong/scheduler-docker-bridge

bug(docker): bind docker bridge to a specific IP