raise correct exception when doing krb5 health check (#14565)

Ensure that failed lookup of kerberos credential allows for us to
perform kerberos recovery steps rather than simply erroring out.

src/middlewared/middlewared/plugins/directoryservices_/kerberos_health_mixin.py

@@ -86,7 +86,7 @@ def _health_check_krb5(self) -> None:
                 faulted_reason
             )
 
-        if not krb5.gss_get_current_cred(krb5_constants.krb5ccache.SYSTEM.value):
+        if not krb5.gss_get_current_cred(krb5_constants.krb5ccache.SYSTEM.value, raise_error=False):
             faulted_reason = (
                 'Kerberos ticket for domain is expired. Failure to renew '
                 'kerberos ticket may indicate issues with DNS resolution or '