Fixing logical error in detecting virtual device.

Redoing my pull request:

So In my Centos 5.9 machine, if there is RAID mount ansible will crash, as it cannot find scheduler file. The reason being, this should be a virtual device as there is no "device" folder under e.g. /sys/block/md0/

Here is the crash:

[kk@u1 ansible]$ ansible q3 -m setup -k -u root --tree=/tmp/facts
SSH password:
q3 | FAILED => failed to parse: /sys/block/md0
Traceback (most recent call last):
  File "/root/.ansible/tmp/ansible-1360629441.14-171498703486275/setup", line 1797, in ?
    main()
  File "/root/.ansible/tmp/ansible-1360629441.14-171498703486275/setup", line 1050, in main
    data = run_setup(module)
  File "/root/.ansible/tmp/ansible-1360629441.14-171498703486275/setup", line 1000, in run_setup
    facts = ansible_facts()
  File "/root/.ansible/tmp/ansible-1360629441.14-171498703486275/setup", line 990, in ansible_facts
    facts.update(Hardware().populate())
  File "/root/.ansible/tmp/ansible-1360629441.14-171498703486275/setup", line 312, in populate
    self.get_device_facts()
  File "/root/.ansible/tmp/ansible-1360629441.14-171498703486275/setup", line 439, in get_device_facts
    m = re.match(".*?(\[(.*)\])", scheduler)
  File "/usr/lib64/python2.4/sre.py", line 129, in match
    return _compile(pattern, flags).match(string)
TypeError: expected string or buffer