IOTHUB_CLIENT_CONNECTION_BAD_CREDENTIAL for missing module, instead of clear reason

[D-r-P-3-p-p-3-r]

Is your feature request related to a problem? Please describe.

If a module doesn't exist, the SDK returns the reason IOTHUB_CLIENT_CONNECTION_BAD_CREDENTIAL.
This makes you look for certificate problems and similar stuff first.

Describe the solution you'd like

A dedicated reason code, if the module does not exist.