generator: run various generators only run on the host, not in initrd

These 5 generators only make sense on the host,not in the initrd, hence
if they end up in the initrd anyway, make them exit quickly.

src/sysv-generator/sysv-generator.c

@@ -14,6 +14,7 @@
 #include "generator.h"
 #include "hashmap.h"
 #include "hexdecoct.h"
+#include "initrd-util.h"
 #include "install.h"
 #include "log.h"
 #include "main-func.h"
@@ -899,6 +900,11 @@ static int run(const char *dest, const char *dest_early, const char *dest_late)
         SysvStub *service;
         int r;
 
+        if (in_initrd()) {
+                log_debug("Skipping generator, running in the initrd.");
+                return EXIT_SUCCESS;
+        }
+
         assert_se(arg_dest = dest_late);
 
         r = lookup_paths_init_or_warn(&lp, RUNTIME_SCOPE_SYSTEM, LOOKUP_PATHS_EXCLUDE_GENERATED, NULL);