workflow: use current copy of repo for docker instead of cloning

docker/melodic/latest/Dockerfile

@@ -1,13 +1,14 @@
 FROM introlab3it/rtabmap:18.04
 
-ARG CACHE_DATE=2016-01-01
-
 RUN source /ros_entrypoint.sh && \
     mkdir -p catkin_ws/src && \
     cd catkin_ws/src && \
-    catkin_init_workspace && \
-    git clone https://github.com/introlab/rtabmap_ros.git && \
-    cd .. && \
+    catkin_init_workspace
+    
+COPY . catkin_ws/src/rtabmap_ros
+
+RUN source /ros_entrypoint.sh && \
+    cd catkin_ws && \
     catkin_make -j1 -DRTABMAP_SYNC_MULTI_RGBD=ON -DCMAKE_INSTALL_PREFIX=/opt/ros/melodic install && \
     cd && \
     rm -rf catkin_ws