Support Storage Template operations in zhmcclient mock support

[andy-maier]

This is to fix the following errors in the "make end2end_mocked" test (as of 2024-06-21):

FAILED tests/end2end/test_storage_group_template.py::test_stogrptpl_find_list[hmc_definition=mocked_hmc_z14] - zhmcclient._exceptions.HTTPError: 404,1: Unknown resource with URI: /api/storage-templates?cpc-uri=%2Fapi%2Fcpcs%2Fcpc_dpm [GET /api/storage-templates?cpc-uri=%2Fapi%2Fcpcs%2Fcpc_dpm]
FAILED tests/end2end/test_storage_group_template.py::test_stogrptpl_property[hmc_definition=mocked_hmc_z14] - zhmcclient._exceptions.HTTPError: 404,1: Unknown resource with URI: /api/storage-templates?cpc-uri=%2Fapi%2Fcpcs%2Fcpc_dpm [GET /api/storage-templates?cpc-uri=%2Fapi%2Fcpcs%2Fcpc_dpm]
FAILED tests/end2end/test_storage_group_template.py::test_stogrptpl_crud[hmc_definition=mocked_hmc_z14] - zhmcclient._exceptions.HTTPError: 404,1: Unknown resource with URI: /api/storage-templates [GET /api/storage-templates]
FAILED tests/end2end/test_storage_group_template.py::test_stogrptpl_find_list[hmc_definition=mocked_hmc_z16] - zhmcclient._exceptions.HTTPError: 404,1: Unknown resource with URI: /api/storage-templates?cpc-uri=%2Fapi%2Fcpcs%2Fcpc_dpm [GET /api/storage-templates?cpc-uri=%2Fapi%2Fcpcs%2Fcpc_dpm]
FAILED tests/end2end/test_storage_group_template.py::test_stogrptpl_property[hmc_definition=mocked_hmc_z16] - zhmcclient._exceptions.HTTPError: 404,1: Unknown resource with URI: /api/storage-templates?cpc-uri=%2Fapi%2Fcpcs%2Fcpc_dpm [GET /api/storage-templates?cpc-uri=%2Fapi%2Fcpcs%2Fcpc_dpm]
FAILED tests/end2end/test_storage_group_template.py::test_stogrptpl_crud[hmc_definition=mocked_hmc_z16] - zhmcclient._exceptions.HTTPError: 404,1: Unknown resource with URI: /api/storage-templates [GET /api/storage-templates]
FAILED tests/end2end/test_storage_volume_template.py::test_stovoltpl_find_list[hmc_definition=mocked_hmc_z14] - zhmcclient._exceptions.HTTPError: 404,1: Unknown resource with URI: /api/storage-templates?cpc-uri=%2Fapi%2Fcpcs%2Fcpc_dpm [GET /api/storage-templates?cpc-uri=%2Fapi%2Fcpcs%2Fcpc_dpm]
FAILED tests/end2end/test_storage_volume_template.py::test_stovoltpl_property[hmc_definition=mocked_hmc_z14] - zhmcclient._exceptions.HTTPError: 404,1: Unknown resource with URI: /api/storage-templates?cpc-uri=%2Fapi%2Fcpcs%2Fcpc_dpm [GET /api/storage-templates?cpc-uri=%2Fapi%2Fcpcs%2Fcpc_dpm]
FAILED tests/end2end/test_storage_volume_template.py::test_stovoltpl_crud[hmc_definition=mocked_hmc_z14] - zhmcclient._exceptions.HTTPError: 404,1: Unknown resource with URI: /api/storage-templates [GET /api/storage-templates]
FAILED tests/end2end/test_storage_volume_template.py::test_stovoltpl_find_list[hmc_definition=mocked_hmc_z16] - zhmcclient._exceptions.HTTPError: 404,1: Unknown resource with URI: /api/storage-templates?cpc-uri=%2Fapi%2Fcpcs%2Fcpc_dpm [GET /api/storage-templates?cpc-uri=%2Fapi%2Fcpcs%2Fcpc_dpm]
FAILED tests/end2end/test_storage_volume_template.py::test_stovoltpl_property[hmc_definition=mocked_hmc_z16] - zhmcclient._exceptions.HTTPError: 404,1: Unknown resource with URI: /api/storage-templates?cpc-uri=%2Fapi%2Fcpcs%2Fcpc_dpm [GET /api/storage-templates?cpc-uri=%2Fapi%2Fcpcs%2Fcpc_dpm]
FAILED tests/end2end/test_storage_volume_template.py::test_stovoltpl_crud[hmc_definition=mocked_hmc_z16] - zhmcclient._exceptions.HTTPError: 404,1: Unknown resource with URI: /api/storage-templates [GET /api/storage-templates]