Rollout don't remove rollouts-pod-template-hash service selector after switching from blue-green to canary strategy

[alexmt]

Rollout don't remove rollouts-pod-template-hash service selector after switching from blue-green to canary strategy.

Steps to reproduce:

1. Deploy rollout with using blue-green strategy
2. Change strategy to canary and update rollout image
3. Rollout deploys canary version as expected but service don't route any traffic to it because it still has rollouts-pod-template-hash service selector which was set during blue-green deployment.

Expected behavior:

Rollout should ensure that rollouts-pod-template-hash service selector is removed unless strategy is blue-green

Version: v0.3.1