UTIL: Use max 15 characters for AD host UPN
We do not want to use host principal with AD
"host/name.domain.tld@DOMAIN.TLD" because it does not work.
We need to use correct user principal for AD hosts. And we cannot
rely all fallback "*$" because of other principals in keytab.
The NetBIOS naming convention allows for 16 characters in a NetBIOS
name. Microsoft, however, limits NetBIOS names to 15 characters and
uses the 16th character as a NetBIOS suffix.
https://support.microsoft.com/en-us/help/163409/netbios-suffixes-16th-character-of-the-netbios-name
Resolves:
https://pagure.io/SSSD/sssd/issue/3329
Reviewed-by: Michal Židek <mzidek@redhat.com>
(cherry picked from commit c6f1bc32774a7cf2f8678499dfbced420be3a3a1)
(cherry picked from commit fee7386e3af5e55eb3c66d8cf3533075b977a734)