Reduce CPU Requests

[eberlep]

Currently, the cpu requests are identical to the cpu limits for the spilo pods.

But since the read-only replicas do not require as much cpu as the primary pod, we can probably safely reduce the cpu requests.

By default, we now set it to 66% of the CPU limit, but that percentage is configurable.

We also check for a certain minimum percentage.

[eberlep]

From one of my test pods:

    Limits:                                                                                                                                                                                                          
      cpu:     500m                                                                                                                                                                                                  
      memory:  2Gi                                                                                                                                                                                                   
    Requests:                                                                                                                                                                                                        
      cpu:      330m                                                                                                                                                                                                 
      memory:   2Gi