fixed inconsistency with check_all_disks naming

The name of the Check for disk space was inconsistend.

In 
./templates/nrpe_cfg/nrpe-check_disk.cfg.erb
it was called check_all_disks_param
but in 
./templates/baseservices.erb
it was called check_all_disks
therefore the template based checks of check_all_disks will fail.