Feature/disable failing model tests

#### Summary:

Attempting to make model tests all pass nearly all the time. I've disabled 3 bugs examples that intermittently fail to converge. The failing tests stops the Jenkins builds.


#### Intended Effect:

The disabled tests are still in place, but are not executed. This will make the model tests pass much more frequently.

#### How to Verify:

Running:
```
make src/test/CmdStan/models
```
should not fail. (Beware, this takes a while)

#### Side Effects:

None.


#### Documentation:

Not user facing.


#### Reviewer Suggestions:

Bob or Michael. We have a few other disabled tests, but at this point, just disabling them is easier than properly fixing them.

At some point, we should revisit all the models. These are easy to find. They can be found be searching for "DISABLED_" in src/test.