dcerpc: invalidate forest trust info cache when filtering out realm domains

When get_realmdomains() method is called, it will filter out subdomains
of the IPA primary domain. This is required because Active Directory
domain controllers are assuming subdomains already covered by the main
domain namespace.

[MS-LSAD] 3.1.4.7.16.1, 'Forest Trust Collision Generation' defines the
method of validating the forest trust information. They are the same as
rules in [MS-ADTS] section 6.1.6. Specifically,

  - A top-level name must not be superior to an enabled top-level name
    for another trusted domain object, unless the current trusted domain
    object has a corresponding exclusion record.

In practice, we filtered those subdomains already but the code wasn't
invalidating a previously retrieved forest trust information.

Fixes: https://pagure.io/freeipa/issue/9551

Signed-off-by: Alexander Bokovoy <abokovoy@redhat.com>
Reviewed-By: Florence Blanc-Renaud <flo@redhat.com>

ipaserver/dcerpc.py

@@ -1103,6 +1103,7 @@ class TrustDomainInstance:
 
         info.count = len(ftinfo_records)
         info.entries = ftinfo_records
+        another_domain.ftinfo_data = info
         return info
 
     def clear_ftinfo_conflict(self, another_domain, cinfo):
@@ -1778,6 +1779,7 @@ class TrustDomainJoins:
             return
 
         self.local_domain.ftinfo_records = []
+        self.local_domain.ftinfo_data = None
 
         realm_domains = self.api.Command.realmdomains_show()['result']
         # Use realmdomains' modification timestamp