Provide --json parameter as an alternative option to --json-file

[snowch]

• https://github.com/hpe-container-platform-community/hpecp-python-library/blob/master/bin/cli.py#L976
• https://github.com/hpe-container-platform-community/hpecp-python-library/blob/master/bin/cli.py#L1011

[snowch]

Until this gets added, a workaround is to use bash process substition <():

hpecp httpclient post /api/v2/worker/k8shost/8 --json-file \
  <(echo '{ "op_spec": { "ephemeral_disks": ["/dev/nvme2n1"]}, "op": "storage"}')