s3-libsmb Don't ever ask for machine$ principals as a target.

s3-libsmb Don't ever ask for machine$ principals as a target.

It is never correct to ask for a machine$ principal as the target of a
kerberos connection.  You should always connect via the
servicePrincipalName.

This current code appears to have built up from a series of minimal
changes, as the codebase adapted the to lack of a SPNEGO principal
from Windows 2008.

Andrew Bartlett

The last two patches address bug #7893 (CIFS tickets vs. <host>$ tickets).
(cherry picked from commit 12bb20a0f6cd85cfdaedf746e7b05416ccde31b0)