pxe & health: Adding hdparm dependency

As i removed the hdparm dep in the base profile, i should add the dep
in the pxe and health profiles.

pxe profile use hdparm to exec an hdparm -t command in the diskinfo.py
file.

  ./src/diskinfo.py:
     return dict((name, parse_hdparm_output(cmd('hdparm -t /dev/%s' % name)))