Put in a caveat about getting the ADT Installer to work
with CentOS 6.x. New note.
Fixes [YOCTO #8324]
(From yocto-docs rev: 6ee7696537ca2031073cc59a42ff035cfd8caeec)
Signed-off-by: Scott Rifenbark <srifenbark@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>