Use GSS_C_NT_HOSTBASED_SERVICE, not GSS_KRB5_NT_PRINCIPAL_NAME

Using `GSS_KRB5_NT_PRINCIPAL_NAME`, and setting the realm to anything other than the empty realm, is a recipe for failure in multi-realm environments.

For example, today I had to debug a case involving three realms, let's call them `AD.FOO.EXAMPLE`, `FOO.EXAMPLE`, and `N.FOO.EXAMPLE`, where on a Linux system `[libdefaults] default_realm = N.FOO.EXAMPLE`, and the SQL Server's principal really is `MSSQLSvc/someserver.ad.foo.example@AD.FOO.EXAMPLE`, but `mssql-cli` constructed a raw Kerberos principal name of the form `MSSQLSvc/someserver.ad.foo.example@`, i.e., `MSSQLSvc/someserver.ad.foo.example@N.FOO.EXAMPLE`. The client credentials we for `user@AD.FOO.EXAMPLE`...

What happened then was that the client fetched a cross-realm TGT, `krbtgt/N.FOO.EXAMPLE@FOO.EXAMPLE` then asked a KDC for `N.FOO.EXAMPLE` for a service ticket for `MSSQLSvc/someserver.ad.foo.example@N.FOO.EXAMPLE`, which yielded a referral to `FOO.EXAMPLE`, which then rejected the request because it would mean doubling back to `AD.FOO.EXAMPLE`, which would be a loop.

Constructing an alternate `krb5.conf` with `[libdefaults] default_realm = AD.FOO.EXAMPLE` and using it by setting the `KRB5_CONFIG` environment variable worked around the problem by causing `mssql-cli` to construct the correct service principal name, `MSSQLSvc/someserver.ad.foo.example@AD.FOO.EXAMPLE`.

If `mssql-cli` had either use `GSS_C_NT_HOSTBASED_SERVICE` and `MSSQLSvc@someserver.ad.foo.example`, or `GSS_KRB5_NT_PRINCIPAL_NAME` and `MSSQLSvc/someserver.ad.foo.example@` (note the "empty" realm), then it would have worked without us having to work around it.

Start by locating where mssql-cli constructs the Kerberos service principal for SQL Server connections. Compare the reported GSS_C_NT_HOSTBASED_SERVICE form with the GSS_KRB5_NT_PRINCIPAL_NAME form using an empty realm, then verify behavior in a multi-realm setup like the one described. Done means the client no longer depends on the configured default realm for this service principal.

Written by the indexing model from the issue text.