Deployment spec properties are inadvertently removed when serializing

## Summary

Various valid deployment spec properties are seemingly wiped out when I load it into a `V1DeploymentSpec` object, make a small change, then re-serialize to a dict.

## Details

I am extracting a `V1DeploymentSpec` from a `ClusterServiceVersion` manifest, making a small mutation to it, then re-serializing it and adding it back into the `ClusterServiceVersion`. This leads to multiple mutations that were not intended. See the following sequence of diffs (none of which were intended) for reference:
```
@@ -356,287 +355,126 @@

- selector:
- matchLabels:
- name: my-operator
+ selector: {}

...

spec:
- affinity:
- nodeAffinity:
- requiredDuringSchedulingIgnoredDuringExecution:
- nodeSelectorTerms:
- - matchExpressions:
- - key: kubernetes.io/arch
- operator: In
- values:
- - s390x
- - amd64
+ affinity: {}

...

- name: WATCH_NAMESPACE
- valueFrom:
- fieldRef:
- fieldPath: metadata.annotations['olm.targetNamespaces']
- name: POD_NAME
- valueFrom:
- fieldRef:
- fieldPath: metadata.name

...

- imagePullPolicy: Always
- livenessProbe:
- failureThreshold: 4
- httpGet:
- path: /healthz
- port: 8081
- initialDelaySeconds: 15
- periodSeconds: 15
- successThreshold: 1
- timeoutSeconds: 3
- readinessProbe:
- failureThreshold: 3
- httpGet:
- path: /healthz
- port: 8081
- initialDelaySeconds: 15
- periodSeconds: 15
- successThreshold: 1
- timeoutSeconds: 3
```