Memory leak in serialized messenger for local sends

[lifflander]

Describe the bug A clear and concise description of what the bug is.

To Reproduce Steps to reproduce the behavior:

1. Example/test/snippet of code that fails
2. Compiler, platform, libraries
3. Run command: number of processors, threading options, etc.
4. See error

Expected behavior A clear and concise description of what you expected to happen.

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Platform (please complete the following information):

• Supercomputer or desktop [e.g., Trinity, Sierra)
• Compiler environment [e.g., clang-4.0, gcc8]
• Libraries [e.g., mpich-2, openmpi)
• Commit ID or release of VT [e.g., vt-1.0.0]

Additional context Add any other context about the problem here.