mss_setup fails with "login_existed" when the existing user is manually deleted (4302247)

When a SQL Server user is created, deleted, and then there is an attempt via mss_setup to create the user again, mss_setup fails stating the user "already existed".

This fails because the master.sys.database_principals table contains orphaned SQL Server users.

The issue occurs in oset/SqlServer/mss_setup.cpp:mss_setup::get_login_name_password():

404 bool login_existed=this->does_login_exist(odbc_drv, splex_user, "master.sys.sql_logins");
405 this->set_login_existed_flag(login_existed);
406 if (false == login_existed)
407

{ 408 login_existed=this->does_login_exist(odbc_drv, splex_user, "master.sys.database_principals"); 409 this->set_login_existed_flag(login_existed); 410 }