re-implement pickValidInfo dataDir, move to quorum calculation (#13681)

dataDir loosely based on maxima is incorrect and does not
work in all situations such as disks in the following order

- xl.json migration to xl.meta there may be partial xl.json's
  leftover if some disks are not yet connected when the disk
  is yet to come up, since xl.json mtime and xl.meta is
  same the dataDir maxima doesn't work properly leading to
  quorum issues.

- its also possible that XLV1 might be true among the disks
  available, make sure to keep FileInfo based on common quorum
  and skip unexpected disks with the older data format.

Also, this PR tests upgrade from older to a newer release if the 
data is readable and matches the checksum.

NOTE: this is just initial work we can build on top of this to do further tests.

buildscripts/minio-upgrade.sh

@@ -0,0 +1,77 @@
+#!/bin/bash
+
+trap 'cleanup $LINENO' ERR
+
+# shellcheck disable=SC2120
+cleanup() {
+    MINIO_VERSION=dev docker-compose \
+                 -f "buildscripts/upgrade-tests/compose.yml" \
+                 rm -s -f
+    docker volume prune -f
+}
+
+__init__() {
+    sudo apt install curl -y
+    export GOPATH=/tmp/gopath
+    export PATH=${PATH}:${GOPATH}/bin
+
+    go install github.com/minio/mc@latest
+
+    TAG=minio/minio:dev make docker
+
+    MINIO_VERSION=RELEASE.2019-12-19T22-52-26Z docker-compose \
+                 -f "buildscripts/upgrade-tests/compose.yml" \
+                 up -d --build
+    until (mc alias set minio http://127.0.0.1:9000 minioadmin minioadmin); do
+        echo "...waiting..." && sleep 5;
+    done
+
+    mc mb minio/minio-test/
+    mc cp ./minio minio/minio-test/to-read/
+    mc cp /etc/hosts minio/minio-test/to-read/hosts
+    mc policy set download minio/minio-test
+    mc cat minio/minio-test/to-read/minio | sha256sum
+    mc cat ./minio | sha256sum
+    curl -s http://127.0.0.1:9000/minio-test/to-read/hosts | sha256sum
+
+    MINIO_VERSION=dev docker-compose -f "buildscripts/upgrade-tests/compose.yml" stop
+}
+
+verify_checksum_after_heal() {
+    sum1=$(curl -s "$2" | sha256sum);
+    mc admin heal --json -r "$1" >/dev/null; # test after healing
+    sum1_heal=$(curl -s "$2" | sha256sum);
+
+    if [ "${sum1_heal}" != "${sum1}" ]; then
+        echo "mismatch expected ${sum1_heal}, got ${sum1}"
+        exit 1;
+    fi
+}
+
+verify_checksum_mc() {
+    expected=$(mc cat "$1" | sha256sum)
+    got=$(mc cat "$2" | sha256sum)
+
+    if [ "${expected}" != "${got}" ]; then
+        echo "mismatch expected ${expected}, got ${got}"
+        exit 1;
+    fi
+}
+
+main() {
+    MINIO_VERSION=dev docker-compose -f "buildscripts/upgrade-tests/compose.yml" up -d --build
+
+    until (mc alias set minio http://127.0.0.1:9000 minioadmin minioadmin); do
+        echo "...waiting..." && sleep 5
+    done
+
+    verify_checksum_after_heal minio/minio-test http://127.0.0.1:9000/minio-test/to-read/hosts
+
+    verify_checksum_mc ./minio minio/minio-test/to-read/minio
+
+    verify_checksum_mc /etc/hosts minio/minio-test/to-read/hosts
+
+    cleanup
+}
+
+( __init__ "$@" && main "$@" )