Usage:
See https://www.tug.org/texlive/doc/tlmgr.html#Pinningtlmgr repository add http://texlive.contextgarden.net/2016-context tlcontext tlmgr repository list tlmgr pinning add tlcontext 'luatex*' tlmgr install --reinstall luatex
tlmgr repository add http://texlive.contextgarden.net/2016-context tlcontext tlmgr repository list tlmgr pinning add tlcontext 'luatex*' tlmgr install --reinstall luatex