build: fix TestS3Minio by pulling minio from quay.io as it has gone from Docker Hub

The minio/minio repository has been removed from Docker Hub so the
TestS3Minio test server could not be started and every Linux CI run
failed. quay.io/minio/minio still serves the final release so use
that instead.

(cherry picked from commit e0d846f29e)

fstest/testserver/init.d/TestS3Minio

@@ -14,7 +14,7 @@ start() {
            -e "MINIO_ACCESS_KEY=$USER" \
            -e "MINIO_SECRET_KEY=$PASS" \
            -p 127.0.0.1:${PORT}:9000 \
-           minio/minio server /data
+           quay.io/minio/minio server /data
     
     echo type=s3
     echo provider=Minio