ca-certificates: run postinst script only for -target package

ca-certificates: run postinst script only for -target package

Nativesdk package has a special arrangement where the same thing is done
in do_install(). It was assumed (in the comment) that postinsts don't run when
installing nativesdk packages, but this was incorrect: they are run, but
any failures were previously silently ignored. Now this missing failure reporting has
been fixed, and so we get to see the failures.

Signed-off-by: Alexander Kanavin <alexander.kanavin@linux.intel.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
(cherry picked from commit 8ebb695c1429f8d57d655072a362a4f176258699)
Signed-off-by: Andreas Oberritter <obi@opendreambox.org>