testsuite: fix expiration propagation test

Problem: The test in t4011-match-duration.t tests that the duration
of a job is inherited from the enclosing instance duration, but we
should really be testing that the *expiration* of a child job is
inherited from the parent when no duration is specified. O/w, a job
submitted when the instance has only a few minutes remaining could
have its expiration set for long after the instance is terminated.

Update the test to ensure that expiration of a job with no duration
specified is inherited from the enclosing instance expiration.
Use flux-alloc(1) to launch the test instance instead of running
standalone flux-start(1) instances even though test_under_flux()
is used.

t/t4011-match-duration.t

@@ -9,17 +9,27 @@ test_description='Test that parent duration is inherited according to RFC14'
 #
 test_under_flux 1
 
-test_expect_success HAVE_JQ 'parent duration is inherited when duration=0' '
+export FLUX_URI_RESOLVE_LOCAL=t
+
+test_expect_success HAVE_JQ 'parent expiration is inherited when duration=0' '
 	cat >get_R.sh <<-EOT &&
 	#!/bin/sh
-
 	flux job info \$FLUX_JOB_ID R
 	EOT
 	chmod +x get_R.sh &&
-	out=$(flux run -t20s -n1 flux start flux run -n1 ./get_R.sh) &&
-	echo "$out" | jq -e ".execution.expiration - .execution.starttime <= 20" &&
-	out=$(flux run -t30s -n1 flux start flux run -n1 ./get_R.sh) &&
-	echo "$out" | jq -e ".execution.expiration - .execution.starttime <= 30"
+	jobid=$(flux alloc -n1 -t5m --bg) &&
+	expiration=$(flux job info $jobid R | jq .execution.expiration) &&
+	test_debug "echo expiration of alloc job is $expiration" &&
+	R1=$(flux proxy $jobid flux run -n1 ./get_R.sh) &&
+	exp1=$(echo "$R1" | jq .execution.expiration) &&
+	test_debug "echo expiration of job is $exp1" &&
+	echo $exp1 | jq ". == $expiration" &&
+	sleep 1 &&
+	R1=$(flux proxy $jobid flux run -n1 ./get_R.sh) &&
+	exp1=$(echo "$R1" | jq .execution.expiration) &&
+	test_debug "echo expiration of second job is $exp1" &&
+	echo $exp1 | jq ". == $expiration" &&
+	flux shutdown --quiet $jobid
 '
 
 test_done