kasli_tester: init urukul channel before calibrating

Otherwise the DDS is not initialized and with a cold system it fails to
find IO_UPDATE edges.

Signed-off-by: Robert Jördens <rj@quartiq.de>

artiq/examples/kasli/repository/kasli_tester.py

@@ -194,6 +194,8 @@ class KasliTester(EnvExperiment):
 
     @kernel
     def calibrate_urukul(self, channel):
+        self.core.break_realtime()
+        channel.init()
         self.core.break_realtime()
         sync_delay_seed, _ = channel.tune_sync_delay()
         self.core.break_realtime()