Make sure to set host_ptr for hostscalations

We need it when we post-process the configuration later, so
it had better be set.

Signed-off-by: Andreas Ericsson <ae@op5.se>

git-svn-id: https://nagios.svn.sourceforge.net/svnroot/nagios/nagioscore/trunk@2710 5f96b256-904b-4d8d-8c98-d829582c6739