Bump XBlock 1.2 testing to version 1.2.2
Bump XBlock 1.2 testing to version 1.2.2

XBlock 1.2.2 was released on 2018-09-07, update the test matrix
to that release for XBlock 1.2.

hastexo/hastexo-xblock,arbrandes/hastexo-xblock,hastexo/hastexo-xblock,hastexo/hastexo-xblock,hastexo/hastexo-xblock,arbrandes/hastexo-xblock,arbrandes/hastexo-xblock,arbrandes/hastexo-xblock,arbrandes/hastexo-xblock