Bug report

Required Info:

• Operating System: Ubuntu 18.04
• Installation type: source
• Version or commit hash: 10d7b7c
• DDS implementation: Fast-RTPS
• Client library (if applicable): rclcpp

Steps to reproduce issue

• Set use_sim_time parameter on a LifecycleNode
• Later, in a message callback, for example, print out the value of node->now()

Expected behavior

The time would be relative to the simulation clock

Actual behavior

It is relative to the system clock