Making str2dicts util function more pythonic and simpler.

With reference to the str2dicts function here https://github.com/apache/libcloud/blob/trunk/libcloud/utils/misc.py#L154

Two suggestions:

• I personally think the "\n\n" is not being taken advantage of.
• Initializing a list and appending a list with empty dict ({}) is not necessary and can be removed. This will allow to remove negative indexing on the list as well.

My thoughts are to change it to look like so:

def str2dicts(data):
   if data is not None and data != "":
        data_blocks = data.split("\n\n")
        line_list = [line.rstrip("\n").lstrip("\n").split("\n") for line in data_blocks]
        return [dict(key_value_string.split(" ") for key_value_string in line) for line in line_list]
    return list({})