Update key pair task:

(1) Check key pair resource duplication
(2) Fix some mistakes
(3) In flow.py, argument "values" contains a dictionary that is taking the resources to be migrated, which are specified by user. 'None' means migrating all resources, a empty list [ ] means migrating nothing.
Merge branch 'master' of https://github.com/Phoenix1708/OpenAcademy_OpenStack_Flyway

Conflicts:
	flyway/flow/usertask.py