Test that cache is created when using single scalar hydrator

[goetas]

Checks that doctrine/dbal#3381 works with the ORM.

This will require most likley to put doctrine/dbal:^2.9.4 (2.9.4 is not yet released)

So not sure if it makes sense (but since orm 2.7 requires at least php 7.2, do not see anything wrong with it)

[goetas]

hmm, something is wrong with my test, https://travis-ci.org/doctrine/orm/jobs/476824447 should be failing

ah, no was introduced in doctrine/dbal#3331 and fixed with doctrine/dbal#3381

so only v2.9.2 v2.9.1 v2.9.0 are affected

[goetas]

BTW doctrine/dbal#3331 is relatively bad as the cache does not keep track of the fetch mode. I think the best thing to do is to revert doctrine/dbal#3331

[goetas]

Ping... nobody here?

[greg0ire]

This will require most likley to put doctrine/dbal:^2.9.4 (2.9.4 is not yet released) So not sure if it makes sense (but since orm 2.7 requires at least php 7.2, do not see anything wrong with it)

IMO it makes sense.