migrate mint tests to latest versions (#9424)

mint/preinstall.sh

@@ -1,6 +1,6 @@
 #!/bin/bash -e
 #
-#  Mint (C) 2017 Minio, Inc.
+#  Mint (C) 2017-2020 Minio, Inc.
 #
 #  Licensed under the Apache License, Version 2.0 (the "License");
 #  you may not use this file except in compliance with the License.
@@ -26,13 +26,19 @@ fi
 
 $APT install apt-transport-https
 
-wget -q https://packages.microsoft.com/config/ubuntu/16.04/packages-microsoft-prod.deb
+if ! $WGET --output-document=packages-microsoft-prod.deb https://packages.microsoft.com/config/ubuntu/18.04/packages-microsoft-prod.deb | bash -; then
+    echo "unable to download dotnet packages"
+    exit 1
+fi
+
 dpkg -i packages-microsoft-prod.deb
 rm -f packages-microsoft-prod.deb
+
 $APT update
+$APT install gnupg ca-certificates
 
 # download and install golang
-GO_VERSION="1.13.5"
+GO_VERSION="1.13.10"
 GO_INSTALL_PATH="/usr/local"
 download_url="https://storage.googleapis.com/golang/go${GO_VERSION}.linux-amd64.tar.gz"
 if ! $WGET --output-document=- "$download_url" | tar -C "${GO_INSTALL_PATH}" -zxf -; then
@@ -42,7 +48,9 @@ fi
 
 xargs --arg-file="${MINT_ROOT_DIR}/install-packages.list" apt --quiet --yes install
 
-# set python 3.5 as default
-update-alternatives --install /usr/bin/python python /usr/bin/python3.5 1
+nuget update -self
+
+# set python 3.6 as default
+update-alternatives --install /usr/bin/python python /usr/bin/python3.6 1
 
 sync