add updating public key (#245)

Author: peifeng-unity

tutorials/pick_and_place/docker/Dockerfile

@@ -1,5 +1,7 @@
 FROM ros:melodic-ros-base
 
+RUN sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys F42ED6FBAB17C654
+
 RUN sudo apt-get update && sudo apt-get install -y vim iputils-ping net-tools python-pip ros-melodic-robot-state-publisher ros-melodic-moveit ros-melodic-rosbridge-suite ros-melodic-joy ros-melodic-ros-control ros-melodic-ros-controllers ros-melodic-tf2-web-republisher dos2unix
 
 RUN sudo -H pip install rospkg jsonpickle