tree-wide: make use of log_error_errno() return value

Turns this:

        r = -errno;
        log_error_errno(errno, "foo");

into this:

        r = log_error_errno(errno, "foo");

and this:

        r = log_error_errno(errno, "foo");
        return r;

into this:

        return log_error_errno(errno, "foo");

src/initctl/initctl.c

@@ -269,8 +269,8 @@ static int server_init(Server *s, unsigned n_sockets) {
 
         s->epoll_fd = epoll_create1(EPOLL_CLOEXEC);
         if (s->epoll_fd < 0) {
-                r = -errno;
-                log_error_errno(errno, "Failed to create epoll object: %m");
+                r = log_error_errno(errno,
+                                    "Failed to create epoll object: %m");
                 goto fail;
         }