Increase test coverage for delete_all when supplying an id instead of an object

[reidmorrison]

This PR reproduces an issue where MultiTenant.with(account) has different behavior from MultiTenant.with(account.id) when calling delete_all or update_all.

Is it expected for the behavior to differ, or should we go ahead and remove the following 2 lines in order to make the behavior consistent for delete_all and update_all?
https://github.com/citusdata/activerecord-multi-tenant/blob/master/lib/activerecord-multi-tenant/relation_extension.rb#L8
And
https://github.com/citusdata/activerecord-multi-tenant/blob/master/lib/activerecord-multi-tenant/relation_extension.rb#L20

[reidmorrison]

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[reidmorrison]

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[reidmorrison]

The tests are now passing locally after these changes made in the PR were merged into master: 20d09a8
Please consider merging this pull request which now only adds tests, since they now include test coverage for the scenario that was fixed.