Fix type mismatch error in tracer_manager test

[J-Lentz]

Description
Fixes a type mismatch error in the tracer_manager test, which causes the test's build to fail with the Cray compiler.

Analogous to PR #1599.

How Has This Been Tested?
tracer_manager test builds and passes with Cray compiler version 18 on C5.

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• Any dependent changes have been merged and published in downstream modules
• New check tests, if applicable, are included
• make distcheck passes