Adapt test fixtures

[TheByronHimes]

Remove the use of the second_s3 fixture from tests. The tests had a flaw with resetting state and the current hexkit fixture setup doesn't allow for multiple containers (this might need to be adapted in the future). The intention with the affected tests in this PR was originally to test potential side effects when multiple storage nodes exist. This could/should be tested with integration tests later, but that still might require the ability to instantiate more than one s3 container.

The changes to both IRS and IFRS tests are basically:

• Remove second_s3 fixture
• Remove for loop in tests iterating through s3/second_s3 fixtures, then unindent everything that was under it (responsible for big change block)
• Only use node1 storage location (did not check super closely for this)
• Move container fixtures to conftest.py in the root test dir for each service
• Move keypair regen and bucket population logic to be outside of joint fixture (now defined in conftest)
• Make joint fixture function scope by default by removing the get_joint_fixture part (and import into conftest so it's always available)
• Remove some pragma statements like F811