Allow dosep.py to print dotest.py output on success.
Previously all test output was reported by each individual
instance of dotest.py. After a recent patch, dosep gets dotest
outptu via a pipe, and selectively decides which output to
This breaks certain scripts which rely on having full output
of each dotest instance to do various parsing and/or log-scraping.
While we make no promises about the format of dotest output, it's
easy to restore this to the old behavior for now, although it is
behind a flag. To re-enable full output, run dosep.py with the -s
Differential Revision: http://reviews.llvm.org/D11816
Reviewed By: Chaoren Lin