Updating pipeline image with necessary libs and bumping up base image version to 20.04LTS (#586)

Co-authored-by: Jaeryn <tsun.chu@microsoft.com>

.pipelines/Dockerfile

@@ -1,18 +1,16 @@
-FROM ubuntu:16.04
-RUN apt-get update && apt-get install -y software-properties-common sudo wget apt-transport-https curl lsb-release gnupg jq
-RUN wget -q https://packages.microsoft.com/config/ubuntu/16.04/packages-microsoft-prod.deb -O packages-microsoft-prod.deb
+FROM ubuntu:20.04
+RUN apt-get update && apt-get install -y software-properties-common sudo wget apt-utils apt-transport-https curl lsb-release gnupg jq
+RUN wget -q https://packages.microsoft.com/config/ubuntu/20.04/packages-microsoft-prod.deb -O packages-microsoft-prod.deb
 RUN sudo dpkg -i packages-microsoft-prod.deb
-RUN add-apt-repository ppa:longsleep/golang-backports 
 RUN curl -sL https://aka.ms/InstallAzureCLIDeb | sudo bash
 RUN curl -fsSL https://get.docker.com -o get-docker.sh && sh get-docker.sh
-RUN apt-get install -y git golang-go=2:1.13~1longsleep1+xenial iptables ipset iproute2 ebtables python-pip gcc zip dotnet-sdk-2.2 azure-cli
-RUN sudo pip install coverage
-RUN if [ -f Gopkg.toml ]; then curl https://raw.githubusercontent.com/golang/dep/master/install.sh | sh ; fi 
+RUN apt install -y git golang-1.14-go iptables ipset iproute2 ebtables python3-pip gcc zip dotnet-sdk-3.1 azure-cli
+RUN apt install -y --no-install-recommends clang cmake zlib1g-dev libboost-dev libboost-thread-dev gdb build-essential libssl-dev
+RUN sudo pip3 install coverage
+ENV PATH="/usr/lib/go-1.14/bin/:${PATH}"
 RUN go get github.com/docker/libnetwork/driverapi
 RUN go get github.com/gorilla/mux
 RUN go get github.com/jstemmer/go-junit-report
 RUN go get github.com/axw/gocov/gocov
 RUN go get github.com/AlekSi/gocov-xml
-RUN go get -u gopkg.in/matm/v1/gocov-html
-ENV PATH="/root/go/bin:${PATH}"
-
+RUN go get -u gopkg.in/matm/v1/gocov-html