test: move sequential/test-signal-unregister

Move sequential/test-signal-unregister to test/parallel, it doesn't
need to run in sequential mode.

PR-URL: https://github.com/iojs/io.js/pull/1227
Reviewed-By: Johan Bergström <bugs@bergstroem.nu>

diff --git a/test/sequential/test-signal-unregister.js b/test/parallel/test-signal-unregister.js
similarity index 100%
rename from test/sequential/test-signal-unregister.js
rename to test/parallel/test-signal-unregister.js