libmount: Fix atime remount for new API

libmount: Fix atime remount for new API

All atime settings are mutually exclusive, and the attr_set mask for
the mount_setattr() syscall cannot contain multiple MOUNT_ATTR_ atime
related options.

Unfortunately, during a remount, the list of options is composed of
both old and new options. In this case, libmount sets more atime
options to the mask. The correct behavior is to use the last atime
related option from the list.

Fixes: https://github.com/util-linux/util-linux/issues/3032
Signed-off-by: Karel Zak <kzak@redhat.com>