Javascript: Adjusting global names of LinkedList solutions so that all the tests can pass

Out of the box, in order to get ```$ mocha --recursive ``` to pass, I needed to change the names of the globals used

```
  $ mocha --recursive

  ․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․

  55 passing (13ms)

```


Adjusting global names of LinkedList solutions so that all the tests can be run and passed otherwise 2_2 clobbers 2_1 and 2_3 clobbers 2_2

Without these changes I got 18 failing tests:

```
$ mocha --recursive --debug-brk
  ․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․

  37 passing (2m)
  18 failing

  1) [object Object] LinkedList deleteDuplicatesA returns 0 length list if 0 length list:
     TypeError: Object #<Object> has no method 'deleteDuplicatesA'
      at Context.<anonymous> (/work/labs/ctci/javascript/test/data-structures/chapter-2/2_1_Spec.js:7:18)
      at callFn (/usr/local/lib/node_modules/mocha/lib/runnable.js:223:21)
      at Test.Runnable.run (/usr/local/lib/node_modules/mocha/lib/runnable.js:2
````