Updated to only inject on non-HHVM

Saw someone else's .travis.yml that opted to not put those extension lines into
the INI when running on HHVM. Worth a shot!

tests/travis.sh

@@ -9,8 +9,9 @@ then
     PHPINI=/etc/hhvm/php.ini
 else
     PHPINI=~/.phpenv/versions/$VERSION/etc/php.ini
-fi
 
     echo "extension = memcache.so"  >> $PHPINI
     echo "extension = memcached.so" >> $PHPINI
     echo "extension = redis.so"     >> $PHPINI
+fi
+