Intermittent Appveyor PR CI failure due to password complexity

Sometimes an Appveyor PR CI will fail, with errors such as

[00:08:02]           WIN32OLERuntimeError:

[00:08:02]             (in OLE method `SetInfo': )

[00:08:02]                 OLE error code:800708C5 in Active Directory

[00:08:02]                   The password does not meet the password policy requirements. Check the minimum password length, password complexity and password history requirements.

[00:08:02]

Typically password complexity is disabled so our tests don't need to worry about it, but for some reason it may become enabled again. This then causes the tests to fail.

It is proposed to modify the failing tests to use complex passwords when creating test user accounts instead of easy or blank passwords.