Mark secondary.kasp test case as flaky on freebsd13

The test_kasp_case[secondary.kasp] can sometimes fail on freebsd13. It
appears the test gets stuck on some operation which should be very
quick, but for some reason takes at least a few seconds, causing the
cb_ixfr_is_signed() function to time out.

In one of the cases I investigated, it wasn't a query/response that
caused a timeout, but rather some operation in between. The test
attempts to read from a keyfile/statefile, but I see no reason why that
should block.

In any case, try to increase the timeout for the verification, as that
shouldn't hurt. Also allow the test to be re-run on freebsd13, as it's
likely to be caused by some odd behaviour on that platform -- the issue
doesn't appear anywhere else.

(cherry picked from commit 126a59cef2)

bin/tests/system/kasp/tests_kasp.py

@@ -203,7 +203,7 @@ def cb_ixfr_is_signed(expected_updates, params, ksks=None, zsks=None):
         )
 
     for update in expected_updates:
-        isctest.run.retry_with_timeout(update_is_signed, timeout=5)
+        isctest.run.retry_with_timeout(update_is_signed, timeout=10)
 
 
 def cb_rrsig_refresh(params, ksks=None, zsks=None):
@@ -586,6 +586,9 @@ def cb_remove_keyfiles(params, ksks=None, zsks=None):
                 ],
             },
             id="secondary.kasp",
+            marks=pytest.mark.flaky(
+                max_runs=2, rerun_filter=isctest.mark.is_host_freebsd_13
+            ),
         ),
         pytest.param(
             {