tree-wide: various code-formatting improvements

Reported/found by Coccinelle

src/basic/alloc-util.c

@@ -78,7 +78,7 @@ void* greedy_realloc(void **p, size_t *allocated, size_t need, size_t size) {
                          * take possession of the extra space. This should be cheap, since libc doesn't have to move
                          * the memory for this. */
 
-                        qq = realloc(q, bn * size);
+                        qq = reallocarray(q, bn, size);
                         if (_likely_(qq)) {
                                 *p = qq;
                                 *allocated = bn;

src/basic/cgroup-util.c

@@ -345,10 +345,8 @@ int cg_kill(
            a workaround for kernel bug. It was fixed in 5.2-rc5 (c03cd7738a83), backported to 4.19.66
            (4340d175b898) and 4.14.138 (feb6b123b7dd). */
         r = cg_unified_controller(controller);
-        if (r < 0)
+        if (r <= 0)
                 return r;
-        if (r == 0) /* doesn't apply to legacy hierarchy */
-                return 0;
 
         return cg_kill_items(controller, path, sig, flags, s, log_kill, userdata, "cgroup.threads");
 }