systemct: show all in output of systemctl clean --what=help

(cherry picked from commit 68b6289)
(cherry picked from commit f9e68aa2b5dd14e0be29d13ea0c45f50bfe6b986)
(cherry picked from commit bf275c73ee0e4293d710b90d467f693eb7d3581b)

Author: behrmann

src/systemctl/systemctl.c

@@ -945,7 +945,8 @@ static int systemctl_parse_argv(int argc, char *argv[]) {
                                              "cache\n"
                                              "logs\n"
                                              "configuration\n"
-                                             "fdstore");
+                                             "fdstore\n"
+                                             "all");
                                         return 0;
                                 }