implement custom puppet support (#6201, #6226)

change puppet command to include in the --modulepath
/srv/leap/files/puppet/modules

If a provider places puppet code under files/puppet it will
be sync'd over to all the nodes, once leap cli #6225 is merged.

The custom puppet entry point is in class 'custom' which can
be put into files/puppet/modules/custom/manifests/init.pp

Change-Id: I74879c6ee056b03cd4691aa81a7668b60383bdad
modify the leap repository contents so they pick the correct repository,
based on the hiera value 'major_version' (#6251)

Change-Id: I10532ef83e3aa2d35d9c0be241952a35e366bba4
Merge "implement custom puppet support (#6201, #6226)" into develop
Merge "modify the leap repository contents so they pick the correct repository, based on the hiera value 'major_version' (#6251)" into develop