Modify azure pipeline to install libyang in azure pipeline steps.#681

liuh-80 merged 3 commits intosonic-net:mastersonic-net/sonic-swss-common:masterfrom

liuh-80:dev/liuh/install-yang-to-pipelineliuh-80/sonic-swss-common:dev/liuh/install-yang-to-pipelineCopy head branch name to clipboard