d/libvirt-clients.manpages: add virkeycode and virkeyname man pages

The old path no more matches anything:
 dh_installman: Cannot find (any matches for) "tools/*.1" (tried in .)
Instead we already have parts of the manpages installed.
In addition we need the virkeycode and virkeyname man pages which so
far were left in the debian/tmp build dir.

Signed-off-by: Christian Ehrhardt <christian.ehrhardt@canonical.com>