[Tests] retry io.js test runs, since iojs.org is flaky.

.travis.yml

@@ -31,7 +31,7 @@ script:
   - if [ -n "${DOCTOCCHECK-}" ]; then cp README.md README.md.orig && npm run doctoc && diff -q README.md README.md.orig ; fi
   - if [ -n "${SHELLCHECK-}" ]; then shellcheck -s bash nvm.sh && shellcheck -s sh nvm.sh && shellcheck -s dash nvm.sh && shellcheck -s ksh nvm.sh ; fi
   - if [ -n "${SHELLCHECK-}" ]; then shellcheck -s bash install.sh bash_completion nvm-exec ; fi
-  - if [ -n "${SHELL-}" ] && [ -n "${TEST_SUITE}" ]; then make TEST_SUITE=$TEST_SUITE URCHIN="$(npm bin)/urchin" test-$SHELL ; fi
+  - if [ -n "${SHELL-}" ] && [ -n "${TEST_SUITE}" ]; then if [ "${TEST_SUITE}" = 'installation_iojs' ]; then travis_retry make TEST_SUITE=$TEST_SUITE URCHIN="$(npm bin)/urchin" test-$SHELL ; else make TEST_SUITE=$TEST_SUITE URCHIN="$(npm bin)/urchin" test-$SHELL; fi; fi
 before_cache:
   - if [ -n "$WITHOUT_CURL" ]; then sudo apt-get install curl -y ; fi
 env: