changes array parameter for /create/image isn't serialized correctly

[Clovel]

I have a bug when using dockerode's importImage function when passing the changes parameter (see apocas/dockerode#785). I found out that the serialization of query strings isn't standard for every parameter.

I found a fix by modifying the Modem.prototype.buildQuerystring function like so :

Modem.prototype.buildQuerystring = function (opts) {
  var clone = {};

  // serialize map and array values as JSON strings, else querystring truncates.
  // 't' and 'extrahosts' can be arrays but need special treatment so that they're
  // passed as multiple qs parameters instead of JSON values.

  console.log(`[DEBUG] <Modem.prototype.buildQuerystring> opts :`, opts);

  Object.keys(opts)
  .map(
    (key, i) => {
      if (
        opts[key] &&
        typeof opts[key] === 'object' &&
        !Array.isArray(opts[key]) &&
        !['t', 'extrahosts'].includes(key)
      ) {
        clone[key] = JSON.stringify(opts[key]);
      } else if (Array.isArray(opts[key])) {
        clone[key] = opts[key]
          .map(
            (val) => {
              if(val && typeof val === 'object') {
                return JSON.stringify(val);
              } else {
                return val;
              }
            }
          );
      } else {
        clone[key] = opts[key];
      }
    }
  );

  const queryStr = querystring.stringify(clone);

  return queryStr;
};

It seems that this is related to #144, so I will try to make the same change.

By not using the JSON syntax for values in the query string, the rest of the dockerode functions I use seem to work fine. I wonder if we should generalize the behaviour of the Modem.prototype.buildQuerystring function for arrays.

[Clovel]

Be removing the else if (Array.isArray(opts[key])) section, the fix still work as expected.

Extensive testing might be needed to ensure there are no breaking changes.