Is it possible to install OLS 1.5.4 from yum repositories

However, this tool is only updating the binary and lswsctrl script at the moment(not all files including VERSION file, so you will still see old over there) and not a full upgrade command yet. We may consider to expand it to a full upgrade tool at later stage.

To reverse back to previous version: it can be done through:
/usr/local/lsws/admin/misc/testbeta -r