[Tests] Add curl back when WITHOUT_CURL test done since cache needs it

.travis.yml

@@ -32,6 +32,8 @@ script:
   - 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-$SHELL ; fi
+after_success:
+  - if [ -n "$WITHOUT_CURL" ]; then sudo apt-get install curl -y ; fi
 env:
   global:
     - CXX=g++-4.8