testsuite: enable sdbus debug logging

Problem: sdbus debug logging is disabled by default, but
this output may be useful in testing.

Enable sdbus-debug in the two sdbus sharness tests.
Also, cover error handling for a bad sdbus-debug config value.

Author: garlick

t/t2407-sdbus.t

@@ -111,9 +111,22 @@ bus_subscribe_cancel () {
     flux python -c "import flux; flux.Flux().rpc(\"sdbus.subscribe-cancel\",{\"matchtag\":$1},flags=flux.constants.FLUX_RPC_NORESPONSE)"
 }
 
+test_expect_success 'enable sdbus-debug in configuration' '
+	flux config load <<-EOT
+	[systemd]
+	sdbus-debug = true
+	EOT
+'
 test_expect_success 'load sdbus module' '
 	flux module load sdbus
 '
+test_expect_success 'sdbus reconfig fails with bad sdbus-debug value' '
+	test_must_fail flux config load <<-EOT 2>config.err &&
+	[systemd]
+	sdbus-debug = 42
+	EOT
+	grep "Expected true or false" config.err
+'
 
 test_expect_success 'sdbus list-units works' '
 	count=$(bus_count_units "*") &&

t/t2408-sdbus-recovery.t

@@ -18,7 +18,13 @@ if ! busctl --user status >/dev/null; then
 	test_done
 fi
 
-test_under_flux 1 minimal
+mkdir -p config
+cat >config/config.toml <<EOF
+[systemd]
+sdbus-debug = true
+EOF
+
+test_under_flux 1 minimal -o,--config-path=$(pwd)/config
 
 flux setattr log-stderr-level 1