Fix empty for loop body

This was actually a real bug - found via travis.

conf.c:878:66: error: for loop has empty body [-Werror,-Wempty-body]

Author: mhaas

src/conf.c

@@ -863,13 +863,13 @@ void parse_trusted_mac_list(const char *ptr) {
 					config.trustedmaclist->next = NULL;
 				} else {
 				/* Advance to the last entry */
-				for (p = config.trustedmaclist; p->next != NULL; p = p->next);
-				p->next = safe_malloc(sizeof(t_trusted_mac));
-				p = p->next;
-				p->mac = safe_strdup(mac);
-				p->next = NULL;
+				for (p = config.trustedmaclist; p->next != NULL; p = p->next) {
+					p->next = safe_malloc(sizeof(t_trusted_mac));
+					p = p->next;
+					p->mac = safe_strdup(mac);
+					p->next = NULL;
+					}
 				}
-			}
 		}
 	}