Barbican client container command error check

Barbican client command to create container does not error if secret ref provided is not as per the convention "name=secretRef". Instead of silently creating the container without the secret ref, we should issue an error.

1) Version of Barbican client: origin/master

2) Steps to reproduce:

~$ barbican secret container create --secret "http://localhost:9311/v1/secrets/2d0a37e2-06b5-4deb-94ef-b43863609bd6"
Starting new HTTP connection (1): localhost
Resetting dropped connection: localhost
+----------------+----------------------------------------------------------------------------+
| Field | Value |
+----------------+----------------------------------------------------------------------------+
| Container href | http://localhost:9311/v1/containers/c4e1aa4e-5e20-4157-b9b0-ec8c3c752a1f |
| Name | None |
| Created | 2016-07-21 07:47:28.258219+00:00 |
| Status | ACTIVE |
| Type | generic |
| Secrets | None |
| Consumers | None |
+----------------+----------------------------------------------------------------------------+