transconf: Fix postinst
transconf: Fix postinst

Postinst script was not using $D as part of the destination path,
and was failing because the build was trying to modify the host
machine paths.

Signed-off-by: Bill Pittman <43ac99c9c99efa205ddaaebf4c7bd970d58e135c@ni.com>
Acked-by: Haris Okanovic <4f2c24956fa4a8756878315db434b9fed29fa615@ni.com>
Acked-by: Alex Stewart <04cdb2793e4fb0120cc30d1c823099f3862701f4@ni.com>
Natinst-ReviewBoard-ID: 314548

ni/meta-nilrt,ni/meta-nilrt,ni/meta-nilrt,ni/meta-nilrt,ni/meta-nilrt