Bayesianoptimization algorithm does not work when hyperparameter are negative doubles

/kind bug

What steps did you take and what happened:

Katib suggest NaN values when submitting an experiment with:

• a parameter with parametertype: double
• a feasibleSpace including negative numbers
• bayesianoptimization as algorithm

For example this kind of yaml makes Katib suggesting NaN for the parameter my-param.

apiVersion: "kubeflow.org/v1alpha3"
kind: Experiment
metadata:
  namespace: kubeflow
  labels:
    controller-tools.k8s.io: "1.0"
  name: my-buggy-experiment
spec:
  objective:
    type: maximize
    goal: 0.99
    objectiveMetricName: my_metric
  algorithm:
    algorithmName: bayesianoptimization
    algorithmSettings:
      - name: "n_initial_points"
        value: "5"
  metricsCollectorSpec:
    collector:
      kind: StdOut
  parallelTrialCount: 1
  maxTrialCount: 2
  maxFailedTrialCount: 3
  parameters:
    - name: --my-param
      parameterType: double
      feasibleSpace:
        min: "-1.0"
        max: "1.0"
trialTemplate:
    goTemplate:
        rawTemplate: |-
          apiVersion: batch/v1
          kind: Job
          metadata:
            name: {{.Trial}}
            namespace: {{.NameSpace}}
          spec:
            template:
              spec:
                containers:
                - name: {{.Trial}}
                  image: some_image
                  command:
                  - "python"
                  - "some_script.py"
                  {{- with .HyperParameters}}
                  {{- range .}}
                  - "{{.Name}}={{.Value}}"
                  {{- end}}
                  {{- end}}
                restartPolicy: Never

What did you expect to happen: Katib should not suggest NaN for my-param but values between -1 and 1.

Anything else you would like to add: Is it due to the log-uniform prior in https://github.com/kubeflow/katib/blob/489d52b0094e36ccb53d26cf0127add9e00bd606/pkg/suggestion/v1alpha3/skopt/base_skopt_service.py line 43?

Environment:

• Kubeflow version: 0.7.0
• Minikube version:
• Kubernetes version: (use kubectl version): 1.14.0
• OS (e.g. from /etc/os-release): Ubuntu 18.04.3 LTS

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[andreyvelich]

That should be fixed as part of: https://github.com/kubeflow/katib/issues/1207.