Bug#168481: libc6.postinst shows dpkg error output

[Adam Heath <doogie@debian.org>]

package: libc6
version: 2.3.1-3

Preparing to replace libc6 2.2.5-14.2 (using .../libc6_2.3.1-3_i386.deb) ...
Unpacking replacement libc6 ...
Setting up libc6 (2.3.1-3) ...
Checking for services that may need to be restarted...Package `logind' is not
installed and no info is available.
Package `apache2' is not installed and no info is available.
Use dpkg --info (= dpkg-deb --info) to examine archive files,
and dpkg --contents (= dpkg-deb --contents) to list their contents.
done.

Please redirect stderr of dpkg to /dev/null.