play kube: optional secrets generate empty environment variable when missing

[ydayagi]

Is this a BUG REPORT or FEATURE REQUEST? (leave only one on its own line)

/kind bug

Description
I have the following PodSpec:

apiVersion: v1
kind: Pod
metadata:
  name: test
spec:
  containers:
  - name: test
    image: quay.io/fedora/fedora:34
    command: [ "/bin/bash", "-c", "--" ]
    args: [ "while true; do sleep 3600; done;" ]
    env:
      - name: SECRET_USERNAME
        valueFrom:
          secretKeyRef:
            name: dummy
            key: username
            optional: true
      - name: SECRET_PASSWORD
        valueFrom:
          secretKeyRef:
            name: mysecret
            key: dummy
            optional: true

I use it with 'podman play kube'.
The secret keys do not exist and are optional in the pod's Spec.
K8S creates a pod without creating the environment variables.
Podman does create the environment variables.
Output of 'env' command in the container:

[root@test_pod /]# env | grep SECRET_
SECRET_USERNAME=
SECRET_PASSWORD=

Steps to reproduce the issue:

Describe the results you received:

Describe the results you expected:

Additional information you deem important (e.g. issue happens only occasionally):

Output of podman version:

podman version 3.3.1

Output of podman info --debug:

host:
  arch: amd64
  buildahVersion: 1.22.3
  cgroupControllers: []
  cgroupManager: systemd
  cgroupVersion: v2
  conmon:
    package: conmon-2.0.27-2.fc33.x86_64
    path: /usr/bin/conmon
    version: 'conmon version 2.0.27, commit: '
  cpus: 8
  distribution:
    distribution: fedora
    version: "33"
  eventLogger: journald
  hostname: localhost.localdomain
  idMappings:
    gidmap:
    - container_id: 0
      host_id: 1000
      size: 1
    - container_id: 1
      host_id: 100000
      size: 65536
    uidmap:
    - container_id: 0
      host_id: 1000
      size: 1
    - container_id: 1
      host_id: 100000
      size: 65536
  kernel: 5.14.11-100.fc33.x86_64
  linkmode: dynamic
  memFree: 28400062464
  memTotal: 32743596032
  ociRuntime:
    name: crun
    package: crun-1.0-1.fc33.x86_64
    path: /usr/bin/crun
    version: |-
      crun version 1.0
      commit: 139dc6971e2f1d931af520188763e984d6cdfbf8
      spec: 1.0.0
      +SYSTEMD +SELINUX +APPARMOR +CAP +SECCOMP +EBPF +CRIU +YAJL
  os: linux
  remoteSocket:
    path: /run/user/1000/podman/podman.sock
  security:
    apparmorEnabled: false
    capabilities: CAP_CHOWN,CAP_DAC_OVERRIDE,CAP_FOWNER,CAP_FSETID,CAP_KILL,CAP_NET_BIND_SERVICE,CAP_SETFCAP,CAP_SETGID,CAP_SETPCAP,CAP_SETUID,CAP_SYS_CHROOT
    rootless: true
    seccompEnabled: true
    seccompProfilePath: /usr/share/containers/seccomp.json
    selinuxEnabled: true
  serviceIsRemote: false
  slirp4netns:
    executable: /usr/bin/slirp4netns
    package: slirp4netns-1.1.12-2.fc33.x86_64
    version: |-
      slirp4netns version 1.1.12
      commit: 7a104a101aa3278a2152351a082a6df71f57c9a3
      libslirp: 4.3.1
      SLIRP_CONFIG_VERSION_MAX: 3
      libseccomp: 2.5.0
  swapFree: 4294963200
  swapTotal: 4294963200
  uptime: 17m 2.24s
registries:
  search:
  - registry.fedoraproject.org
  - registry.access.redhat.com
  - docker.io
store:
  configFile: /home/ydayagi/.config/containers/storage.conf
  containerStore:
    number: 2
    paused: 0
    running: 2
    stopped: 0
  graphDriverName: overlay
  graphOptions: {}
  graphRoot: /home/ydayagi/.local/share/containers/storage
  graphStatus:
    Backing Filesystem: btrfs
    Native Overlay Diff: "true"
    Supports d_type: "true"
    Using metacopy: "false"
  imageStore:
    number: 2
  runRoot: /run/user/1000/containers
  volumePath: /home/ydayagi/.local/share/containers/storage/volumes
version:
  APIVersion: 3.3.1
  Built: 1630356406
  BuiltTime: Mon Aug 30 23:46:46 2021
  GitCommit: ""
  GoVersion: go1.15.14
  OsArch: linux/amd64
  Version: 3.3.1

Package info (e.g. output of rpm -q podman or apt list podman):

podman-3.3.1-1.fc33.x86_64

Have you tested with the latest version of Podman and have you checked the Podman Troubleshooting Guide? (https://github.com/containers/podman/blob/master/troubleshooting.md)

Yes/No

Additional environment details (AWS, VirtualBox, physical, etc.):

[rhatdan]

@umohnani8 PTAL