dpkg: Use less as pager

dpkg: Use less as pager

Debian traditionaly uses /usr/bin/pager as the system pager, which is a
link to the user preferred pager. This is a Debianism.

Without this patch:

root@qt5122:~# dpkg -l
sh: pager: command not found
dpkg-query: error: showing package list on pager subprocess returned error exit status 127

Signed-off-by: Ricardo Ribalda Delgado <ricardo@ribalda.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>