Change bind result with NULL dn and non NULL password

[progier389]

Issue Description
We should change the simple bind result when no DN is specified but a password is specified.
The behavior of this case is not specified by RFC 4513
So actual result (handling it as an anonymous bind) is not really a bug, but returning INVALID_CREDENTIAL would be better as it would avoid buggy application to consider that it authenticates successfully while it just bind anonymously.

Package Version and Platform:

• Platform: Fedora
• Package and version: Any version
• Browser: N/A

Steps to Reproduce
Steps to reproduce the behavior:

1. Use python ldap to perform a simple bind with no DN but a password
2. Result is SUCCESS instead of INVALID_CREDENTIAL

Expected results
Should get INVALID_CREDENTIAL and be bound anonymously (as usual after a bind failure)

Additional context
Jira issue: IDM-7181