made namespace in receiver launch script a parameter

[tobi807]

Need to start 2 Can Receiver (2x PCAN) in one launch script and wanted to keep the supplied receiver launch file.

<launch>

  <arg name="receiver_interval_sec" default="5.0" />
  <arg name="enable_can_fd" default="false" />
  <arg name="use_bus_time" default="false" />
  <arg name="channel_0_name" default="can0_msg" />
  <arg name="channel_1_name" default="can1_msg" />

  <include file="$(find-pkg-share ros2_socketcan)/launch/socket_can_receiver.launch.py">
    <arg name="namespace" value="can0" />
    <arg name="interface" value="can0" />
    <arg name="interval_sec" value="$(var receiver_interval_sec)" />
    <arg name="enable_can_fd" value="$(var enable_can_fd)" />
    <arg name="from_can_bus_topic" value="$(var channel_0_name)" />
    <arg name="use_bus_time" value="$(var use_bus_time)" />
  </include>

  <include file="$(find-pkg-share ros2_socketcan)/launch/socket_can_receiver.launch.py">
    <arg name="namespace" value="can1" />
    <arg name="interface" value="can1" />
    <arg name="interval_sec" value="$(var receiver_interval_sec)" />
    <arg name="enable_can_fd" value="$(var enable_can_fd)" />
    <arg name="from_can_bus_topic" value="$(var channel_1_name)" />
    <arg name="use_bus_time" value="$(var use_bus_time)" />
  </include>

</launch>

They ended up with the same name in the same namespace. My solution is to move them in different namespace, and I did that by modifying the receiver launch file to accept the namespace as parameter from the parant launch file. Not sure if it is the ros way. If there is a better way please discard the pull request.