[PATCH] tweak node unlink handling

[PATCH] tweak node unlink handling

Based on a patch from Olaf Hering we remove the node now only if the
requested dev_t is different from the already existing node, so any
run of udevstart should preserve the inode number of the node file.

syslog while the right node is already there:
  creating device node '/udev/hda'
  make_node: preserve file '/udev/hda', cause it has correct dev_t
  make_node: chmod(/udev/hda, 060600)

syslog for wrong file already there:
  creating device node '/udev/hda'
  make_node: already present file '/udev/hda' unlinked
  make_node: chmod(/udev/hda, 060600)

syslog for directory with same name already there:
  creating device node '/udev/hda'
  make_node: unlink(/udev/hda) failed with error '21'