exit-status: kill is_clean_exit_lsb(), move logic to sysv-generator

Let's get rid of is_clean_exit_lsb(), let's move the logic for the special
handling of the two LSB exit codes into the sysv-generator by writing out
appropriate SuccessExitStatus= lines if the LSB header exists. This is not only
semantically more correct, bug also fixes a bug as the code in service.c that
chose between is_clean_exit_lsb() and is_clean_exit() based this check on
whether a native unit files was available for the unit. However, that check was
bogus since a long time, since the SysV generator was introduced and native
SysV script support was removed from PID 1, as in that case a unit file always
existed.

src/sysv-generator/sysv-generator.c

@@ -25,6 +25,7 @@
 
 #include "alloc-util.h"
 #include "dirent-util.h"
+#include "exit-status.h"
 #include "fd-util.h"
 #include "fileio.h"
 #include "hashmap.h"
@@ -199,6 +200,13 @@ static int generate_unit_file(SysvStub *s) {
         if (s->pid_file)
                 fprintf(f, "PIDFile=%s\n", s->pid_file);
 
+        /* Consider two special LSB exit codes a clean exit */
+        if (s->has_lsb)
+                fprintf(f,
+                        "SuccessExitStatus=%i %i\n",
+                        EXIT_NOTINSTALLED,
+                        EXIT_NOTCONFIGURED);
+
         fprintf(f,
                 "ExecStart=%s start\n"
                 "ExecStop=%s stop\n",