Fix iam create-virtual-mfa-device to work with relative output paths.

This commit also cleans up some of the test module code including:

* pep8 formatting
* remove unused imports
* switchover to assert_params_for_cmd2.
Add issue to changelog
Merge branch 'quiver-fix-iam-CreateVirtualMFADevice-for-relative-outfile-path' into develop

* quiver-fix-iam-CreateVirtualMFADevice-for-relative-outfile-path:
  Add issue to changelog
  Fix iam create-virtual-mfa-device to work with relative output paths.