Add simulation tests

Use clknetsim to run multiple chronyd instances with simulated clocks
and network. It allows fast and reproducible testing, without real
network.

Included are several tests of performance in different clock/network
conditions, chronyd options, NTP authentication, chronyc, and past bug
fixes.

test/simulation/103-initstepslew

@@ -0,0 +1,32 @@
+#!/bin/bash
+
+. test.common
+test_start "initstepslew directive"
+
+freq_offset=0.0
+wander=0.0
+limit=100
+
+# clknetsim requires source port (if bound) to match dest port
+client_server_options="port 124"
+client_conf="initstepslew 5 192.168.123.1
+port 124"
+
+min_sync_time=15
+max_sync_time=30
+
+for time_offset in -2.0 -0.2 0.2 2.0; do
+	run_test || test_fail
+	check_chronyd_exit || test_fail
+	check_sync || test_fail
+done
+
+min_sync_time=1
+max_sync_time=1
+
+for time_offset in -1e8 -1e2 1e2 1e8; do
+	run_test || test_fail
+	check_sync || test_fail
+done
+
+test_pass