Find all buildout configs in a subdirectory.
    only buildout.cfg and etc/buildout.cfg are valid in::

    path
        directory where to start to search

    cfg
        a optional list to append to

            .
            ├── buildout.cfg
            ├── etc
            │   └── buildout.cfg
            ├── foo
            │   └── buildout.cfg
            └── var
                └── buildout.cfg

def _find_cfgs(path, cfgs=None):
    '''
    Find all buildout configs in a subdirectory.
    only buildout.cfg and etc/buildout.cfg are valid in::

    path
        directory where to start to search

    cfg
        a optional list to append to

            .
            ├── buildout.cfg
            ├── etc
            │   └── buildout.cfg
            ├── foo
            │   └── buildout.cfg
            └── var
                └── buildout.cfg
    '''
    ignored = ['var', 'parts']
    dirs = []
    if not cfgs:
        cfgs = []
    for i in os.listdir(path):
        fi = os.path.join(path, i)
        if fi.endswith('.cfg') and os.path.isfile(fi):
            cfgs.append(fi)
        if os.path.isdir(fi) and (i not in ignored):
            dirs.append(fi)
    for fpath in dirs:
        for p, ids, ifs in salt.utils.path.os_walk(fpath):
            for i in ifs:
                if i.endswith('.cfg'):
                    cfgs.append(os.path.join(p, i))
    return cfgs