mktemp: lower the priority of standalone mktemp package

mktemp: lower the priority of standalone mktemp package

Lower the priority of the standalone mktemp package, so that
finally the mktemp command installed into SDK image is
coreutils.mktemp.

coreutils.mktemp is widely extended to support more feature,
and could not break some existing scripts and common usecases.

For example: at least three 'X's, and mktemp XXX.pdf(do not
have to be the trailing character for 'X')

Signed-off-by: Zhixiong Chi <Zhixiong.Chi@windriver.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>