Merge "fs_mgr: overlayfs: if existing scratch mountpoint is system_empty"

    auto mnt_type = fs_mgr_overlayfs_scratch_mount_type();

    if (partition_exists) {

        if (fs_mgr_overlayfs_mount_scratch(scratch_device, mnt_type)) {

            if (!fs_mgr_access(kScratchMountPoint + kOverlayTopDir) &&

                !fs_mgr_filesystem_has_space(kScratchMountPoint)) {

                // declare it useless, no overrides and no free space

                fs_mgr_overlayfs_umount_scratch();

            } else {

                if (change) *change = true;

                return true;

            }

        }

        // partition existed, but was not initialized; fall through to make it.

        errno = 0;

    }