docker prefer copy to add (#1250)

Signed-off-by: Mai Bui <maibui@microsoft.com>
#### Why I did it
Docker best practices prefer COPY to ADD
https://docs.docker.com/develop/develop-images/dockerfile_best-practices/#add-or-copy
##### Work item tracking
- Microsoft ADO **(number only)**: 17418730
#### How I did it
Use the COPY command as opposed to ADD unless working with a tar file.

.azure-pipelines/docker-sonic-vs/Dockerfile

@@ -3,7 +3,7 @@ FROM docker-sonic-vs
 ARG docker_container_name
 ARG need_dbg
 
-ADD ["debs", "/debs"]
+COPY ["debs", "/debs"]
 
 RUN dpkg -i /debs/libswsscommon_1.0.0_amd64.deb \
             /debs/python3-swsscommon_1.0.0_amd64.deb \