If evergreen expansions are used in the "resmoke_args" that burn_in_test uses, they don't get expanded which causes burn_in_test to fail when it runs.

Example:

Patch Build: https://mongodbcr.appspot.com/224090001/#msg5

Evergreen Failure: https://evergreen.mongodb.com/task/mongodb_mongo_master_enterprise_rhel_62_64_bit_burn_in_tests_patch_d5c06c53024f5d9d35135248dbdf833459aace37_5c054ae3e3c331655283c904_18_12_03_15_25_36