Set default for -iness probe parameters and add docs

[rooftopcellist]

SUMMARY

We did not have a default set for the following variables, which caused errors in some situations.

web_liveness_period: 0
web_readiness_period: 0
task_liveness_period: 0
task_readiness_period: 0

This PR fixes that. More info on the original issue in the section below.

ISSUE TYPE

• Bug, Docs Fix or other nominal change

Problem statement

I don't set a spec at all:

apiVersion: awx.ansible.com/v1beta1
kind: AWX
metadata:
name: awx
namespace: awx
But if I have like:

---
apiVersion: awx.ansible.com/v1beta1
kind: AWX
metadata:
  name: awx
  namespace: awx
spec:
  no_log: true

It will auto-gen with this:

spec:
  admin_user: admin
  auto_upgrade: true
  create_preload_data: true
  garbage_collect_secrets: false
  image_pull_policy: IfNotPresent
  ipv6_disabled: false
  loadbalancer_class: ""
  loadbalancer_ip: ""
  loadbalancer_port: 80
  loadbalancer_protocol: http
  metrics_utility_cronjob_gather_schedule: '@hourly'
  metrics_utility_cronjob_report_schedule: '@monthly'
  metrics_utility_enabled: false
  metrics_utility_pvc_claim_size: 5Gi
  no_log: false
  postgres_keepalives: true
  postgres_keepalives_count: 5
  postgres_keepalives_idle: 5
  postgres_keepalives_interval: 5
  projects_persistence: false
  projects_storage_access_mode: ReadWriteMany
  projects_storage_size: 8Gi
  replicas: 1
  route_tls_termination_mechanism: Edge
  set_self_labels: true
  task_liveness_failure_threshold: 3
  task_liveness_initial_delay: 5
  task_liveness_period: 0
  task_liveness_timeout: 1
  task_privileged: false
  task_readiness_failure_threshold: 3
  task_readiness_initial_delay: 20
  task_readiness_period: 0
  task_readiness_timeout: 1
  web_liveness_failure_threshold: 3
  web_liveness_initial_delay: 5
  web_liveness_period: 0
  web_liveness_timeout: 1
  web_readiness_failure_threshold: 3
  web_readiness_initial_delay: 20
  web_readiness_period: 0
  web_readiness_timeout: 1