Merge branch 'travis_cleanup' of https://github.com/sitsofe/fio

* 'travis_cleanup' of https://github.com/sitsofe/fio:
  Makefile: fix incorrectly set libiscsi cflags
  memory: fix incorrect pointer comparison when freeing cuda memory
  travis: make CI install script bail out on first error
  travis: enable libiscsi and cuda ioengines
  travis: add dependency for cuda ioengine
  travis: use install section instead of before_install section
  configure: check for Debian/Ubuntu tcmalloc_minimal
  travis: improve installation dependencies
  travis: simplify yml file