Fixing Firedrake tests (#537)

* Changed to new name of Firedrake docker image

* Removed venv stuff

* Added different venv

* Added some debug info

* Changed python version

* Changed pip

* added debug output

* trying different install of pytest

* trying different pytest

* Fixed tests

* Fixed more tests

* Yet more fix. This time it will totally work, I am like 1000% sure

* Increased number of available tasks

* Increased one more tolerance

* Got rid of OMPI_UNIVERSE thing

* Needed to add one more oversubscribe

* Put oversubscribe in wrong place