euca-describe-addresses fails with missing attribute on Address object

Stacktrace:

 File "/opt/local/bin/euca-describe-addresses-2.7", line 41, in <module>
    cmd.main_cli()
  File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/euca2ools/commands/euca/describeaddresses.py", line 63, in main_cli
    self.display_addresses(addresses)
  File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/euca2ools/commands/euca/describeaddresses.py", line 50, in display_addresses
    domain = address.domain or 'standard'
None

euca2ools Version 2.0.0, Python 2.7, Mac OS X (10.7.2), boto 2.0

Fix:

euca2ools/commands/euca/describeaddresses.py: line 50

Replace:

                domain = address.domain or 'standard'

With:
                domain = getattr(address, "domain", None)
                if not domain: domain = "standard"

I wasn't sure if this was (perhaps) a change in the bot API for the address object or not, so I just replaced with a getattr call and a default return of None...which we can then test and assign the default domain string "standard".

This would cover the explicit case currently in the code and the special case, resulting in this bug, of an undefined attribute.