function _cmdCloseServer(path, cba) {
    var pathKey = getPathKey(path);
    if (_servers[pathKey]) {
        var serverToClose = _servers[pathKey];
        delete _servers[pathKey];
        serverToClose.close();
        return true;
    }
    return false;
}
@private
Handler function for the staticServer.closeServer command. If a server
exists for the given path, closes it, otherwise does nothing. Note that
this function doesn't wait for the actual socket to close, since the
server will actually wait for all client connections to close (which can
be awhile); but once it returns, you're guaranteed to get a different
server the next time you call getServer() on the same path.

@param {string} path The absolute path whose server we should close.
@return {boolean} true if there was a server for that path, false otherwise