Cleanup temporary parameter files when passing parameter dict to Node actions

[dhood]

Parameters can be passed to Node actions as dictionaries as of ros2/launch#138. This is done by writing a temporary parameter yaml file. The temporary file's name should be kept track of and deleted on shutdown to avoid files taking up too much space (hypothetically, in the case where nodes are set to respawn on shutdown, if there's an error that keeps restarting the node, many files could be generated (depending on how it's implemented)).

This task is a followup from https://github.com/ros2/launch/pull/138/files#diff-d78062ac1f3a77c95190e470302b7e69R188.

[dhood]

Also, tests added in that PR check the resulting files so an opt-out option for cleanup woupd be appropriate there