Bug 1045421 - Remove date time bomb from test_crash_manager.js, add logging. r=gfritzsche, a=test-only

There was a hard-coded date in test_crash_manager.js of around August 3,
2013. This meant that about a year later we would start to run into
boundary issues since we weren't wrapping Date.now() inside
CrashManager.jsm.

It turns out the actual value of DUMMY_DATE doesn't really matter. So,
the test has been changed to produce a value that is reasonably modern.

While I was debugging this, I noticed we're not getting logging in the
tests. So I added that.