Allow sssd read symlinks in /etc/sssd

Previously, sssd was allowed to read only plain configuration files in
/etc/sssd. Since this commit it is allowed to read symlinks, too, which
supports a scenario where sssd_auth_ca_db.pem points to /etc/ipa/ca.crt
so that cert renewals are automatically picked up, with no
administrative overhead.

Resolves: SSSD/sssd#6611

policy/modules/contrib/sssd.te

@@ -76,6 +76,7 @@ allow sssd_t self:unix_stream_socket { create_stream_socket_perms connectto };
 allow sssd_t sssd_exec_t:file execute_no_trans;
 
 read_files_pattern(sssd_t, sssd_conf_t, sssd_conf_t)
+read_lnk_files_pattern(sssd_t, sssd_conf_t, sssd_conf_t)
 list_dirs_pattern(sssd_t, sssd_conf_t, sssd_conf_t)
 
 manage_dirs_pattern(sssd_t, sssd_public_t, sssd_public_t)