chore(ci) fix OpenSSL install (outdated version)

Thanks OpenSSL for not having a channel with both old and new releases
:(

.travis.yml

@@ -14,7 +14,7 @@ env:
     - LUA_VERSION=luajit-2.1
     - CASSANDRA_VERSION=2.2.4
     - LUAROCKS_VERSION=2.2.2
-    - OPENSSL_VERSION=1.0.2e
+    - OPENSSL_VERSION=1.0.2f
     - OPENRESTY_VERSION=1.9.3.1
     - SERF_VERSION=0.7.0
     - DNSMASQ_VERSION=2.75
@@ -56,4 +56,4 @@ cache:
     - $OPENRESTY_DIR
     - $SERF_DIR
     - $DNSMASQ_DIR
-    - $HOME/.ccm/repository
+    - $HOME/.ccm/repository