Only display running instances in the list for the associate IP dialog
Plus added try and except blocks for the associate IP operations
Added more try and expect blocks for boto calls
Leanred that IP addresses weren't loading when connected to AWS due to the type mismatch between '' and None, that are different from Eucalyptys and AWS.
Minor whitespace fix for PEP8
Merge pull request #195 from eucalyptus/GUI-395

Only display running instances in the list for the associate IP dialog