path: minor refactoring

1) This uses some ternary expressions instead of if else to assign
   some variables.
2) Use template strings instead of concat.
3) Use the object shortand notation.
4) Some var to let / const.
5) Removed some double line breaks.
6) Less brackets around statements if not necessary.

PR-URL: https://github.com/nodejs/node/pull/25278


Reviewed-By: Michaël Zasso <targos@protonmail.com>