Add RHEL6 support

- package python-ordereddict required to run
- package python-unittest2 to run unnittest
- new run_test to use unit2
- qemu-system has another name on RHEL6
- decorators to make the tests compatible with python 2.6

Signed-off-by: Eduardo Elias Ferreira <edusf@linux.vnet.ibm.com>