API endpoint "network prune" returns array of objects instead of array of string

[arctic-alpaca]

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

/kind bug

Description Hi, the API reference for prune networks describes the response as array of strings. It actually returns a Array of objects.

Steps to reproduce the issue:

1. podman system service unix:///home/`whoami`/testing.sock --log-level=debug --time=500

2. podman network create

3. 
   curl -X POST --unix-socket /home/`whoami`/testing.sock "http://d/v3.2.0/libpod/networks/prune"
   [{"Name":"cni-podman0","Error":null},{"Name":"cni-podman1","Error":null}] 

Describe the results you received: Array of objects.

Describe the results you expected: An array of strings.

Output of podman version:

Version:      3.2.0
API Version:  3.2.0
Go Version:   go1.15.10
Git Commit:   0281ef262dd0ffae28b5fa5e4bdf545f93c08dc7-dirty
Built:        Tue Jan  1 01:00:00 1980
OS/Arch:      linux/amd64

Output of podman info --debug:

host:
  arch: amd64
  buildahVersion: 1.21.0
  cgroupControllers: []
  cgroupManager: cgroupfs
  cgroupVersion: v1
  conmon:
    package: 'conmon: /usr/libexec/podman/conmon'
    path: /usr/libexec/podman/conmon
    version: 'conmon version 2.0.27, commit: '
  cpus: 12
  distribution:
    distribution: debian
    version: "10"
  eventLogger: file
  hostname: DESKTOP
  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: 5.4.72-microsoft-standard-WSL2
  linkmode: static
  memFree: 12699619328
  memTotal: 13346447360
  ociRuntime:
    name: crun
    package: 'crun: /usr/bin/crun'
    path: /usr/bin/crun
    version: |-
      crun version 0.18.1-7931a-dirty
      commit: 7931a1eab0590eff4041c1f74e2844b297c31cea
      spec: 1.0.0
      +SYSTEMD +SELINUX +APPARMOR +CAP +SECCOMP +EBPF +CRIU +YAJL
  os: linux
  remoteSocket:
    path: /tmp/podman-run-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: false
  serviceIsRemote: false
  slirp4netns:
    executable: /usr/bin/slirp4netns
    package: 'slirp4netns: /usr/bin/slirp4netns'
    version: |-
      slirp4netns version 1.1.8
      commit: unknown
      libslirp: 4.3.1-git
      SLIRP_CONFIG_VERSION_MAX: 3
      libseccomp: 2.4.4
  swapFree: 4294967296
  swapTotal: 4294967296
  uptime: 3h 6m 47.76s (Approximately 0.12 days)
registries:
  search:
  - docker.io
  - quay.io
store:
  configFile: /home/alpaca/.config/containers/storage.conf
  containerStore:
    number: 4
    paused: 0
    running: 0
    stopped: 4
  graphDriverName: overlay
  graphOptions:
    overlay.mount_program:
      Executable: /usr/bin/fuse-overlayfs
      Package: 'fuse-overlayfs: /usr/bin/fuse-overlayfs'
      Version: |-
        fusermount3 version: 3.4.1
        fuse-overlayfs: version 1.4
        FUSE library version 3.4.1
        using FUSE kernel interface version 7.27
  graphRoot: /home/alpaca/.local/share/containers/storage
  graphStatus:
    Backing Filesystem: extfs
    Native Overlay Diff: "false"
    Supports d_type: "true"
    Using metacopy: "false"
  imageStore:
    number: 15
  runRoot: /tmp/podman-run-1000/containers
  volumePath: /home/alpaca/.local/share/containers/storage/volumes
version:
  APIVersion: 3.2.0
  Built: 315532800
  BuiltTime: Tue Jan  1 01:00:00 1980
  GitCommit: 0281ef262dd0ffae28b5fa5e4bdf545f93c08dc7-dirty
  GoVersion: go1.15.10
  OsArch: linux/amd64
  Version: 3.2.0

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

Static version from: https://github.com/containers/podman/runs/2740486864

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

Additional environment details (AWS, VirtualBox, physical, etc.): Windows 10, 64bit, WLS2, Debian 10

[rhatdan]

@Luap99 PTAL