service: preserve explicit stop for remain tasks

A completed remain task unconditionally cleared its user stop block
after running its post script.  Since it was still valid in the current
runlevel, it immediately started again, making initctl stop ineffective.

Keep explicit stops blocked, distinguish automatic and requested
restarts, and route initctl restart through teardown before rerunning the
task.  Cover stop, start, restart, reload, and runlevel transitions with
a regression test.

Signed-off-by: zhangxiaohui <xiaohui.zhang@wbstar.com>

test/remain-task-control.sh

@@ -0,0 +1,76 @@
+#!/bin/sh
+
+set -eu
+
+TEST_DIR=$(dirname "$0")
+TEST_CONF=/etc/finit.d/remain-task.conf
+STATE=/run/remain-task.state
+
+test_teardown()
+{
+    run "rm -f $TEST_CONF $STATE"
+}
+
+assert_runs()
+{
+    assert "Remain task has run $1 time(s)" \
+           "$(texec initctl -j status remain-task | jq -M .restarts)" -eq "$1"
+}
+
+# shellcheck source=/dev/null
+. "$TEST_DIR/lib/setup.sh"
+
+say 'Add remain task'
+run "cat > $TEST_CONF" <<EOF
+task remain-task {
+    description       = "Remain task control"
+    runlevel          = "2345"
+    remain-after-exit = true
+    command           = "/bin/touch $STATE"
+    exec-stop-post    = "/bin/rm -f $STATE"
+}
+EOF
+run "initctl reload"
+
+retry 'assert_status remain-task done'
+assert_file_exists "$STATE"
+assert_runs 1
+
+say 'Stop remain task'
+run "initctl stop remain-task"
+retry 'assert_status remain-task stopped'
+assert "Post script removed state" \
+       "$(texec sh -c "[ ! -e '$STATE' ] && echo yes")" = yes
+assert_runs 1
+
+say 'Start remain task'
+run "initctl start remain-task"
+retry 'assert_status remain-task done'
+assert_file_exists "$STATE"
+assert_runs 2
+
+say 'Restart remain task'
+run "initctl restart remain-task"
+retry 'assert_runs 3'
+retry 'assert_status remain-task done'
+assert_file_exists "$STATE"
+
+say 'Reload changed remain task'
+run "sed -i 's/Remain task control/Updated remain task control/' $TEST_CONF"
+run "initctl reload"
+retry 'assert_runs 4'
+retry 'assert_status remain-task done'
+assert_file_exists "$STATE"
+
+say 'Leave remain task runlevel'
+run "initctl runlevel 1"
+retry 'assert_status remain-task halted'
+assert "Post script removed state" \
+       "$(texec sh -c "[ ! -e '$STATE' ] && echo yes")" = yes
+assert_runs 4
+
+say 'Re-enter remain task runlevel'
+run "initctl runlevel 2"
+retry 'assert_runs 5'
+retry 'assert_status remain-task done'
+assert_file_exists "$STATE"