Add env var to set network ranges used by tests

Adds
 POOL_DEFAULT which will set the value for all other networks if not
  defined
 POOL_ADMIN, POOL_PUBLIC, POOL_MANAGEMENT, POOL_PRIVATE, POOL_STORAGE which will set their respective network ranges.

This is needed so that test setups can easily have seperate network ranges
 so external routing can be controlled.

Closes-bug #1266539

Change-Id: I38168d52e959051530f2d18329d7241e9e0e47fa