Fix `RabbitMQ` output path

[yczhang-nv]

Description

The examples in examples/developer_guide/2_2_rabbitmq and 4_rabbitmq_cpp_stage do not generate output files to $MORPHEUS_ROOT when following the README guidance. Change the output path to the root of repo to be consistent with other examples.

Closes #1754

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• I am familiar with the Contributing Guidelines.
• When the PR is ready for review, new or existing tests cover these changes.
• When the PR is ready for review, the documentation is up to date with these changes.

[dagardner-nv]

/merge