Install libyang to azure pipeline (#310)

Author: liuh-80

azure-pipelines.yml

@@ -38,6 +38,7 @@ steps:
     sudo dpkg -i libnl-route-3-200_*.deb
     sudo dpkg -i libnl-nf-3-200_*.deb
     sudo dpkg -i libhiredis0.14_*.deb
+    sudo dpkg -i libyang_1.0.73_amd64.deb
     sudo dpkg -i libswsscommon_1.0.0_amd64.deb
     sudo dpkg -i python-swsscommon_1.0.0_amd64.deb
     sudo dpkg -i python3-swsscommon_1.0.0_amd64.deb