Test coverage on ARMv7 / ARMv8

[leezu]

Description

Virtualized (qemu-based) testing of ARMv7 and ARMv8 has been simplified as part of fb73a17

The test coverage has not been extended as part of the PR and only the executor level tests are run:
python3 -m nose --verbose tests/python/unittest/test_engine.py (this is run in unittest_ubuntu_python3_arm)

The runtime of the ARM testing stage has been greatly reduced as part of the commit (from over 1 hour to around 3 minutes) and we can thus extend the test coverage without concerns about slowing down development.

CC @mseth10 as this is related to your work on Jetson. Essentially all CPU level tests can probably be run using qemu and you only need to run GPU level tests on an actual device.