[BUG] - instances.updateInstance() does not work correctly

[gabos31]

Describe the bug

1. Error in the code

   vultr-node/src/util.js

   Line 47 in a7aa8c6

   (newObj, key) => Object.assign(newObj, { [key]: parameters[key] }),

   
   should be: (newObj, key) => Object.assign(newObj, { [key]: userParameters[key] }),
2. Parameters that are passed empty (''), for example, the security group from which you want to exclude the instance, are not included in the request body. This is due to a parameter validation error.
   For example, this can be avoided by adding an additional condition to

   vultr-node/src/index.js

   Line 61 in a7aa8c6

   } else if (userParameter) {

   
   should be: } else if (userParameter || userParameter === '') {

[ddymko]

@gabos31 Thanks for reporting the issues! Feel free to submit PRs to fix them if you want.

[gabos31]

@ddymko I created a PR, but there are some problems with checks. #452