test: move some test from sequential to parallel

The only test with modifications is `test-stdin-child-proc` that was
passing when it should not because the exit code of the child process
was not being checked.

PR-URL: #6087
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Johan Bergström <bugs@bergstroem.nu>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Sakthipriyan Vairamani <thechargingvolcano@gmail.com>
Reviewed-By: Claudio Rodriguez <cjrodr@yahoo.com>

Author: santigimeno

test/sequential/test-debug-args.js renamed to test/parallel/test-debug-args.js

@@ -17,4 +17,3 @@ child.on('exit', function(code, signal) {
   assert.equal(code, 0);
   assert.equal(output, 'hello, world!\n');
 });
-

test/sequential/test-force-repl-with-eval.js renamed to test/parallel/test-force-repl-with-eval.js

@@ -27,4 +27,3 @@ server.listen(common.PORT, function() {
 process.on('exit', function() {
   assert.ok(accepted);
 });
-