[Tests] travis-ci: fix SSL

Hopefully fixes iojs.org issues with LetsEncrypt expiration; this is
travis-ci's suggestion

.travis.yml

@@ -14,8 +14,7 @@ cache:
     - $TRAVIS_BUILD_DIR/.cache
     - $TRAVIS_BUILD_DIR/node_modules
 before_install:
-  - sudo sed -i 's/mozilla\/DST_Root_CA_X3.crt/!mozilla\/DST_Root_CA_X3.crt/g' /etc/ca-certificates.conf
-  - sudo update-ca-certificates -f
+  - sudo apt update && sudo apt install libgnutls-openssl27 libgnutls30 && sudo apt-get update && sudo apt-get install apt-transport-https ca-certificates -y && sudo update-ca-certificates
   - $SHELL --version 2> /dev/null || dpkg -s $SHELL 2> /dev/null || which $SHELL
   - curl --version
   - wget --version