Enable DPB dependency check using YANG model in VS container (#45) (#4990)

Added required packages to enabled YANG dependency check for Dynamic Port Breakout in VS container.

[sonic-utilities PR #766](https://github.com/Azure/sonic-utilities/pull/766) has a dependency on it.
Getting error like the following without this fix: `ImportError: No module named yang - required module not found`

Signed-off-by: Sangita Maity <sangitamaity0211@gmail.com>

platform/vs/docker-sonic-vs.mk

@@ -7,7 +7,10 @@ $(DOCKER_SONIC_VS)_DEPENDS += $(SWSS) \
                               $(PYTHON_SWSSCOMMON) \
                               $(LIBTEAMDCTL) \
                               $(LIBTEAM_UTILS) \
-                              $(SONIC_DEVICE_DATA)
+                              $(SONIC_DEVICE_DATA) \
+                              $(LIBYANG) \
+                              $(LIBYANG_CPP) \
+                              $(LIBYANG_PY2)
 
 $(DOCKER_SONIC_VS)_PYTHON_DEBS += $(SONIC_UTILS)
 

platform/vs/docker-sonic-vs/Dockerfile.j2

@@ -60,6 +60,7 @@ RUN pip install crontab
 # Install dependencies for Dynamic Port Breakout
 RUN pip install xmltodict==0.12.0
 RUN pip install jsondiff==1.2.0
+RUN pip install ijson==2.6.1
 
 {% if docker_sonic_vs_debs.strip() -%}
 # Copy locally-built Debian package dependencies