Fix the bug in double-ring case where Priam is confused as the replace address case.
Add more waited time if Priam is bootstrapping C* with a new IP as SG needs some time to get updated by other seeds.
Fix get_seeds REST API to return a seed if its instance id is valid
Provide a function to check whether an instance is a dummy one
Merge pull request #321 from timiblossom/1.2

Mostly for double-ring bug fix