salt.sh: Drop upstream clone in favor of local git

salt.sh: Drop upstream clone in favor of local git

salt.sh currently clones the full Fuel@OPNFV git repo from upstream
public mirror, preventing us from testing locally edited or new
patches.

Instead, bring back git submodule handling from old f_repos, clone
and patch each submodule locally, then copy the whole parent repo
over to cfg01.

This is also a first step towards implementing offline deploy support.

NOTE: This adds new deploy prerequisite packages:
- git (for submodule clone/update);
- make (for submodule patching);
- rsync (for parent repo replication to cfg01);

NOTE: Parent repository is expected to be a git repo, in order to
work with git submodules.

While at it, perform some minor related changes:
- add deploy artifacts (ISOs, qcow2 files) to .gitignore, also used
  to filter-out such files during rsync to cfg01;
- remove obsolete Fuel patches (old f_repos mechanism);
- rename "reclass-system-salt-model" submodule;

Change-Id: I6210d80d41010b2802e4f1b31acf249a18db7963
Signed-off-by: Alexandru Avadanii <Alexandru.Avadanii@enea.com>