Fix Cozy Monitor install

there is a bug in the current version of
`fabtools.nodejs.package_version()`, used by the
`fabtools.require.nodejs.package()` function, which has been fixed in
the git repository but is not yet present in the release (see
https://github.com/ronnix/fabtools/commit/45fdb3a2bed6798afa80fa4fe7bd284c55b67862).
I switched back to the old installation method, until the fix is
released.