Autodetection of distro is done after config file creation

[asmodehn]

Autodetection should happen before, so that the config fil already contains the detected distro name, instead of 'unknown' as it is currently.

WARNING:pyros_interfaces_ros:loading pyros_setup and configuring your ROS environment
WARNING:pyros_config.confighandler:Default configuration has been generated in /home/alexv/.virtualenvs/rostful_rostest/var/pyros_setup-instance/pyros_setup.cfg
WARNING:pyros_setup:Dynamic PyROS setup starting...
WARNING:pyros_setup.ros_setup: => Pyros_setup v0.2.1 Emulating ROS setup now for distro unknown and workspaces ()
WARNING:pyros_setup.ros_setup:Prepending path /opt/ros/melodic/share to ROS_PACKAGE_PATH
WARNING:pyros_setup.ros_setup:Prepending path /opt/ros/melodic/bin to PATH
WARNING:pyros_setup.ros_setup:Prepending path /opt/ros/melodic/lib to LD_LIBRARY_PATH
WARNING:pyros_setup.ros_setup:Prepending path /opt/ros/melodic/lib/pkgconfig to PKG_CONFIG_PATH
WARNING:pyros_setup.ros_setup:Prepending path /opt/ros/melodic/lib/python2.7/dist-packages to sys.path
Re-adding /opt/ros/melodic/lib/python2.7/dist-packages in front of sys.path
WARNING:pyros_setup.ros_setup: => ROS setup emulation done.
WARNING:pyros_setup:Dynamic PyROS setup done.

# default configuration generated by pyros-setup
# Usage from python :
# import pyros_setup
# pyros_setup.configurable_import().configure().activate()
#
# Fill in your workspaces here, if you want to dynamically import ROS packages from it.
WORKSPACES=[]

# ROS distribution. Change this value to the ROS distribution you want to use with this environment.
DISTRO='unknown'