Add missing rollout strategy for deployment

[phoenix-bjoern]

The deployment.yaml doesn't have a rollout strategy. The defaults however could lead to issues with replicas <= 2:

  strategy:
    rollingUpdate:
      maxSurge: 25%
      maxUnavailable: 25%
    type: RollingUpdate

Therefore the rollout strategy should be configurable with safe defaults, e.g.

    strategy:
      rollingUpdate:
        maxSurge: 1
        maxUnavailable: 0
      type: RollingUpdate