Note that replicas: 1 does not actually guarantee "at most 1". If you have block storage with locks (AWS/gce/ceph/cinder), then he second replica won't start until the first is gone. If you try to use "replicas: 1" with a shared filesystem you can have 2 pods running against that filesystem at once.
That's solved by setting "strategy.type" to "Recreate", isn't it? This will disable rolling deploys. The replication controller wouldn't then attempt to have two pods running at the same time.
