Ensure JSInput tests actually run

This test currently fails, meaning that the existing tests weren't
testing what they claimed.

Assertions are made for each element returned by the CSS selectors.
However, the selectors are assumed to be wildcard matches, but are
actually literal selectors. As there are no matched elements, this
causes the assertions to be (silently) checked zero times, without
failure.
Fix JSInput tests

Select DOM elements with wildcard syntax

- DOM lookups were being done with non-existent literal selectors, so it
  was returning empty lists. As assertions were to be made while
  iterating over the list of elements, nothing was actually being
  verified.

- Common code has been centralized in the setup function. By declaring
  CSS selectors once, we minimize the odds of inadvertently using the
  wrong selector, as happened here.

- Had these tests actually been iterating over a non-empty list, this
  would have thrown undefined exceptions. jQuery.each calls its handler
  with an index and an item/object as the arguments. However, the object
  is a DOM-object, not a jQuery-object.  These tests break, as they had
  assumed the latter.
Remove superfluous JSInput test

The behavior previously tested here was to check that if a JSInput
element was marked as not processed, re-walking the DOM *should* have
reinitialized it. Unfortunately, this behavior is not supported by the
underlying JSChannel library. In fact, if JSChannel detects an existing
channel with the same origin and scope, it throws an uncaught exception,
leaving the DOM in a "broken" state.

JSInput will prevent duplicates from being added, as long as we don't
manually update the `data-processed` attribute. This behavior is already
being tested.
Fix JSInput test fixture

Clean up fixtures automatically between tests
- Nesting test fixture markup within a DIV allows Jasmine to
  automatically restore the fixture to a clean state between each test
  run.

Fix id attribute collision typo
- This looks like a copy/pasta gone wrong; the two test INPUT elements
  were both declared with the same id, `input_1`.

Remove trailing whitespace
Fix JSInput scope leak

Declare variables locally
- The `allSections` variable was leaking into the global scope, due to a
  typo in the declaration.
- `dataProcessed` can be declared more narrowly within the callback.
Merge pull request #4008 from edx/stv/jsinput

Fix Jasmine tests for JSInput