Use spotbugs instead of findbugs. Removed findbugs from the hadoop build images,
and added spotbugs in the images instead.
Reviewed-by: Masatake Iwasaki <iwasakims@apache.org>
Reviewed-by: Inigo Goiri <inigoiri@apache.org>
Reviewed-by: Dinesh Chitlangia <dineshc@apache.org>