Fix a udev / grub problem
See https://bugs.launchpad.net/ubuntu/+source/grub2/+bug/604335
      https://bugs.launchpad.net/ubuntu/+source/grub2/+bug/565146
      http://lists.opensuse.org/opensuse-bugs/2012-04/msg00301.html
Clean up imports and various other smaller items

- Import OzException directly instead of referencing the full package name
- Import various os.path and oz.ozutil functions to more readable and shorter lines
- Replace multiple write() calls with a single multi line write() call
wrong serial port

Conflicts:
	oz/Ubuntu.py