Allow omitting -machines flag in apiserver when -cloud_provider and
-minion_regexp are specified because it is eventually overwritten by
-minion_regexp.
Merge pull request #716 from yugui/fix/machines-flag

Allow omitting -machines flag in apiserver
FakeEtcdClient: Maintain change index
Generate modification index only if f.TestIndex is specified.
This is for compatibility with existing tests.
Fail immediately if f.Err is set
return EtcdErrorNodeExist when Create is called for existing node
Implement FakeEtcdClient.CompareAndSwap
AtomicUpdate should use api.Encode
Implement FakeEtcdClient.ExpectNotFoundGet
Add test for AtomicUpdate