core: when determining whether a process exit status is clean, consider whether it is a command or a daemon

SIGTERM should be considered a clean exit code for daemons (i.e. long-running
processes, as a daemon without SIGTERM handler may be shut down without issues
via SIGTERM still) while it should not be considered a clean exit code for
commands (i.e. short-running processes).

Let's add two different clean checking modes for this, and use the right one at
the appropriate places.

Fixes: #4275

src/basic/exit-status.c

@@ -177,17 +177,17 @@ const char* exit_status_to_string(int status, ExitStatusLevel level) {
         return NULL;
 }
 
-bool is_clean_exit(int code, int status, ExitStatusSet *success_status) {
+bool is_clean_exit(int code, int status, ExitClean clean, ExitStatusSet *success_status) {
 
         if (code == CLD_EXITED)
                 return status == 0 ||
                        (success_status &&
                        set_contains(success_status->status, INT_TO_PTR(status)));
 
-        /* If a daemon does not implement handlers for some of the
-         * signals that's not considered an unclean shutdown */
+        /* If a daemon does not implement handlers for some of the signals that's not considered an unclean shutdown */
         if (code == CLD_KILLED)
-                return IN_SET(status, SIGHUP, SIGINT, SIGTERM, SIGPIPE) ||
+                return
+                        (clean == EXIT_CLEAN_DAEMON && IN_SET(status, SIGHUP, SIGINT, SIGTERM, SIGPIPE)) ||
                         (success_status &&
                          set_contains(success_status->signal, INT_TO_PTR(status)));