url: change scoping of variables with let

[kthelgason]

This PR addresses variable redeclarations in lib/url.js by changing hoisted vars to let.
Also changes some vars to const as recommended by the linter.

@Trott points out in #4853 that the linter reports a lot of redeclarations. I believe addressing this incrementally is easier and less risky, hence this PR only fixes these issues in this one file.

[tflanagan]

I'm confused as to what made you change var to let or const, you are changing some but not all. I understand the changes in the for loops, but it seems you are leaking beyond that scope.

IE: Line 674, authInHost

[kthelgason]

I tried to handle all cases where a variable was redeclared. The for loop scopes were obvious, but there were also some other cases, like the one you mention, authInHost. I could have been more clear on that in the description.

[Trott]

CI: https://ci.nodejs.org/job/node-test-pull-request/1378/

[Trott]

LGTM if CI is OK

[Trott]

@tflanagan If it's useful, here's the eslint report that @kthelgason was probably looking at to decide which instances in the file to change. https://gist.github.com/Trott/7dc16adf550b6a8d06cc

[kthelgason]

@Trott @tflanagan yes that is indeed the report I was looking at.
The CI fails building on Ubuntu15.04, any idea what might be wrong?

[Trott]

@kthelgason It looks like a problem with the CI host itself and not anything in your code. Will run CI again so we can hopefully see green on Ubuntu 15.04 and declare victory.

CI again: https://ci.nodejs.org/job/node-test-pull-request/1380/

[Trott]

CI is green. LGTM

[jasnell]

LGTM

[Trott]

Landed in fcae05e