Update global-jjb install instructions to symlink the jjb and shell
directories in global-jjb and clone the submodule to the root of
ci-management instead.
This allows us to use tools that have YAML file configurations that
JJB will otherwise pick up and parse as invalid JJB config.
Issue: RELENG-1204
Change-Id: I5060dd0c1b67fa020a84844936eebb970ae2cbb6
Signed-off-by: Thanh Ha <thanh.ha@linuxfoundation.org>