s4-dsdb: Extended samdb.newuser to accept security descriptor for the object and...

s4-dsdb: Extended samdb.newuser to accept security descriptor for the object and optionally skip password reset

Sometimes for testing purposes we create users without any permissions on their objects and password reset
cannot be performed at that point, and is not necessary. For this purpose we can now optionally skip this step.
The default is still to reset the user password.
Also, a security.descriptor object can be specified during the user creation to override using the default one.
defaultSecurityDescriptor is still used by default.