Cleanup JUnit reporter based on suggestions from ESLint

[astorije]

I know you aren't using ESLint, but as we were monkey-patching this file and I linted it on our end, I figured I should send these your way.
I tried to remove the opinionated/stylistic ones and only keep those who do improve the code.

These fix the following:

2:1   error  Move the invocation into the parens that contain the function  wrap-iife
35:29  error  Unnecessary escape character: \&                               no-useless-escape
37:23  error  Unnecessary escape character: \>                               no-useless-escape
38:23  error  Unnecessary escape character: \"                               no-useless-escape
39:23  error  Unnecessary escape character: \'                               no-useless-escape
54:5   error  Expected line before comment                                   lines-around-comment
60:12  error  Unary word operator 'typeof' must be followed by whitespace    space-unary-ops
60:18  error  Gratuitous parentheses around expression                       no-extra-parens
63:36  error  Move the invocation into the parens that contain the function  wrap-iife
73:27  error  Move the invocation into the parens that contain the function  wrap-iife
182:24  error  Unary word operator 'typeof' must be followed by whitespace    space-unary-ops
182:30  error  Gratuitous parentheses around expression                       no-extra-parens
183:31  error  Unary word operator 'typeof' must be followed by whitespace    space-unary-ops
183:37  error  Gratuitous parentheses around expression                       no-extra-parens
197:49  error  'specName' is defined but never used                           no-unused-vars
212:13  error  'totalSpecsExecuted' is defined but never used                 no-unused-vars
213:13  error  'totalSpecsDefined' is defined but never used                  no-unused-vars
230:40  error  'summary' is defined but never used                          no-unused-vars
234:73  error  'encoding' is defined but never used                         no-unused-vars
480:38  error  Gratuitous parentheses around expression                       no-extra-parens
236:83  error  'fd' is defined but never used                                 no-unused-vars
316:20  error  Unnecessary 'else' after 'return'                              no-else-return
366:1   error  Trailing spaces not allowed                                    no-trailing-spaces
394:20  error  Unnecessary 'else' after 'return'                              no-else-return
428:1   error  Trailing spaces not allowed                                    no-trailing-spaces

[astorije]

Hey folks, are you any interested by this PR? :)

[putermancer]

I'd happily merge this PR if the same changes were applied to the rest of the reporter files. As it is now, it only cleans up the junit reporter, but several of the same items exist in nunit and others. While I like cleanliness and things that pass linters, in this case I prefer things that are consistent within the repo. So if you want to update the PR with similar cleanup for the rest of the reporter files, I'm happy to merge.

[putermancer]

I'm happy to merge this if all the reporter files are updated similarly, but would rather keep them consistent than change one to use new patterns in isolation.

[astorije]

Hey @bloveridge! This PR is quite outdated with a bunch of conflicts, so I'll do so in a new PR for history sake.