everywhere: always use O_CLOEXEC where it makes sense

src/shared/fileio.c

@@ -130,7 +130,7 @@ ssize_t sendfile_full(int out_fd, const char *fn) {
         assert(out_fd > 0);
         assert(fn);
 
-        f = fopen(fn, "r");
+        f = fopen(fn, "re");
         if (!f)
                 return -errno;
 

src/shared/sleep-config.c

@@ -174,7 +174,7 @@ static int hibernation_partition_size(size_t *size, size_t *used) {
         assert(size);
         assert(used);
 
-        f = fopen("/proc/swaps", "r");
+        f = fopen("/proc/swaps", "re");
         if (!f) {
                 log_full(errno == ENOENT ? LOG_DEBUG : LOG_WARNING,
                          "Failed to retrieve open /proc/swaps: %m");