regular expression fails if name is defined

Hi,
In:
https://github.com/eucalyptus/eutester/blob/testing/eucaops/ec2ops.py#L2083

If name is defined emi could remain set to None which makes the regular expression:

if (re.search(emi, image.id) is None) and (re.search(emi, image.name) is None):

fails.

might be good to set the emi="mi-" by default in the args defintion and delete:

if name is None:
    emi="-mi"
