Improve test coverage for tranformsLinkNodeToOembedNode.js

[nickytonline]

Description

Currently, code coverage for tranformsLinkNodeToOembedNode.js is pretty low (63.64%). Not that we're striving for 100% code coverage, but looking at it, it seems like the coverage could go up drastically if other branches in the code of that file are hit during tests.

-----------------------------------|----------|----------|----------|----------|-------------------|
File                               |  % Stmts | % Branch |  % Funcs |  % Lines | Uncovered Line #s |
-----------------------------------|----------|----------|----------|----------|-------------------|
All files                          |    97.01 |    92.86 |      100 |     96.9 |                   |
 utils                             |    96.97 |    92.86 |      100 |    96.85 |                   |
  amendOptions.js                  |      100 |      100 |      100 |      100 |                   |
  amendProviders.js                |      100 |      100 |      100 |      100 |                   |
  fetchOembed.js                   |      100 |      100 |      100 |      100 |                   |
  fetchOembedProviders.js          |      100 |      100 |      100 |      100 |                   |
  filterProviderKeys.js            |      100 |      100 |      100 |      100 |                   |
  filterProviders.js               |      100 |      100 |      100 |      100 |                   |
  getProviderEndpointForLinkUrl.js |      100 |    92.86 |      100 |      100 |                10 |
  logResults.js                    |      100 |      100 |      100 |      100 |                   |
  prepublish.js                    |      100 |      100 |      100 |      100 |                   |
  selectPossibleOembedLinkNodes.js |      100 |      100 |      100 |      100 |                   |
  tranformsLinkNodeToOembedNode.js |    63.64 |       25 |      100 |    63.64 |       10,11,12,19 |
 utils/.test                       |      100 |      100 |      100 |      100 |                   |
  markdown.js                      |      100 |      100 |      100 |      100 |                   |
  providers.js                     |      100 |      100 |      100 |      100 |                   |
-----------------------------------|----------|----------|----------|----------|-------------------|
Test Suites: 11 passed, 11 total