Use juju-qa-test in bundle tests

[barrettj12]

#15453 and #15460 tried to fix the deploy bundles tests, without success. Unfortunately, the tiny-bash charm doesn't support arm64, so we'll switch to the juju-qa-test charm which does.

QA steps

Check the bundles tests now pass.

cd tests
./main.sh -v \
  -s '"test_cmr_bundles_export_overlay,test_deploy_charms,test_deploy_default_series,test_deploy_os,test_deploy_revision,run_deploy_lxd_profile_bundle_openstack,run_deploy_lxd_profile_bundle"' \
  deploy test_deploy_bundles

TODO

• Test on amd64
• Test on arm64

[barrettj12]

There is no latest/stable release of juju-qa-test for arm64 focal, so we'll use latest/candidate instead.

[nvinuesa]

LGTM, thanks!

[barrettj12]

/merge