nspawn, machine-id-setup: warn if read-only mount call fails

They are not crucial, but they shouldn't fail.

src/core/machine-id-setup.c

@@ -235,7 +235,9 @@ int machine_id_setup(void) {
                 log_info("Installed transient /etc/machine-id file.");
 
                 /* Mark the mount read-only */
-                mount(NULL, "/etc/machine-id", NULL, MS_BIND|MS_RDONLY|MS_REMOUNT, NULL);
+                if (mount(NULL, "/etc/machine-id", NULL,
+                          MS_BIND|MS_RDONLY|MS_REMOUNT, NULL) < 0)
+                        log_warning("Failed to make transient /etc/machine-id read-only");
         }
 
 finish:

src/nspawn/nspawn.c

@@ -537,8 +537,8 @@ static int setup_boot_id(const char *dest) {
         if (mount(from, to, "bind", MS_BIND, NULL) < 0) {
                 log_error("Failed to bind mount boot id: %m");
                 r = -errno;
-        } else
-                mount(from, to, "bind", MS_BIND|MS_REMOUNT|MS_RDONLY, NULL);
+        } else if (mount(from, to, "bind", MS_BIND|MS_REMOUNT|MS_RDONLY, NULL))
+                log_warning("Failed to make boot id read-only: %m");
 
         unlink(from);
         return r;