tls: fix handling of asterisk in SNI context

Wildcard server names should not match subdomains.

Quote from RFC2818:

   ...Names may contain the wildcard
   character * which is considered to match any single domain name
   component or component fragment. E.g., *.a.com matches foo.a.com but
   not bar.foo.a.com. f*.com matches foo.com but not bar.com.

fix #6610