The order of the keys from the data store is not prescribed. If
target_datadir comes before datadir the selftests fail since the 'wrong'
variable is used for substitutions. This highlights an issue with the
replace_dir_vars() function. Fix this.
(From OE-Core rev: d47c496aa058f5b18d03a68bcd79e5c8607de34f)
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>