Investigate test flakiness:
DevMode#doStartUpServer() fails from time to time (rarely) due
to an unknown error. Adding some logging to pinpoint the problem

Review at http://gwt-code-reviews.appspot.com/1401803

Review by: fabbott@google.com

git-svn-id: https://google-web-toolkit.googlecode.com/svn/trunk@9943 8db76d5a-ed1c-0410-87a9-c151d255dfc7