tests: Run Valgrind memory-leak checks for C++ Unit Tests on Travis CI.
test: Added valgrind suppressions for getpwnam_r

https://sourceware.org/bugzilla/show_bug.cgi?id=2314
http://stackoverflow.com/questions/188591/is-there-a-fix-or-a-workaround-for-the-memory-leak-in-getpwnam
Merge branch 'master' into jdillmann-travis_valgrind
Merge branch 'jdillmann-travis_valgrind'
tests: delete Hadoop tarballs after extracting
tests: Fix xtestenv progress for volume tests.
tests: updated Hadoop version in test script