Improve robustness of init test

By adding an additional synchronization point in the form of a matched
log message, this patch makes the timing behavior of the "test changing
provided services" step more deterministic. Without it, the scheduling
of OKL4 and base-hw resulted in a merge of two config updates into one.

Issue #3079

repos/os/recipes/raw/test-init/test-init.config

@@ -293,7 +293,7 @@
 		<start name="log">
 			<binary name="dummy"/>
 			<resource name="RAM" quantum="1M"/>
-			<config/>
+			<config> <log string="no service yet"/> </config>
 			<route> <any-service> <parent/> </any-service> </route>
 		</start>
 		<start name="dummy">
@@ -305,6 +305,7 @@
 			</route>
 		</start>
 	</init_config>
+	<expect_log string="[init -> log] no service yet"/>
 	<sleep ms="1000"/>
 	<expect_init_state>
 		<node name="child"> <attribute name="name" value="log"/> </node>