Replaced concatenated strings with template literals in the configfile.js

[ghost]

updates: haraka/Haraka#2129

[codecov]

Codecov Report

Merging #34 into master will not change coverage.
The diff coverage is 28.57%.

@@           Coverage Diff           @@
##           master      #34   +/-   ##
=======================================
  Coverage   81.54%   81.54%           
=======================================
  Files           8        8           
  Lines         428      428           
  Branches      124      124           
=======================================
  Hits          349      349           
  Misses         79       79

Impacted Files	Coverage Δ
configfile.js	70.24% <28.57%> (ø)	⬆️

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