Add functional API tests for volume connector and volume target

Extend baremetal json client with volume connector and volume target.
Add basic positive tests for volume connector and volume target:

    test_create_volume_connector_error
    test_delete_volume_connector
    test_delete_volume_connector_error
    test_show_volume_connector
    test_list_volume_connectors
    test_list_with_limit
    test_update_volume_connector_replace
    test_update_volume_connector_replace_error
    test_update_volume_connector_remove_item
    test_update_volume_connector_remove_collection
    test_update_volume_connector_add

    test_create_volume_target_error
    test_delete_volume_target
    test_delete_volume_target_error
    test_show_volume_target
    test_list_volume_targets
    test_list_with_limit
    test_update_volume_target_replace
    test_update_volume_target_replace_error
    test_update_volume_target_remove_item
    test_update_volume_target_remove_collection
    test_update_volume_target_add

Change-Id: I642a02cff2afe7f89b6800d69e14d05e04e6a59c
Partial-bug: #1559691
4 files changed