[CI] Pass cloud cache secrets to linux wheel (ray-project#6232)

.travis.yml

@@ -116,7 +116,7 @@ matrix:
  # For the linux wheel build, we use a shared cache between all
  # wheels, but not between different travis runs, because that
  # caused timeouts in the past. See the "cache: false" line below.
- - export MOUNT_BAZEL_CACHE="-v $HOME/ray-bazel-cache:/root/ray-bazel-cache -e TRAVIS=true -e TRAVIS_PULL_REQUEST=$TRAVIS_PULL_REQUEST"
+ - export MOUNT_BAZEL_CACHE="-v $HOME/ray-bazel-cache:/root/ray-bazel-cache -e TRAVIS=true -e TRAVIS_PULL_REQUEST=$TRAVIS_PULL_REQUEST -e encrypted_1c30b31fe1ee_key=$encrypted_1c30b31fe1ee_key -e encrypted_1c30b31fe1ee_iv=$encrypted_1c30b31fe1ee_iv"
 
  # This command should be kept in sync with ray/python/README-building-wheels.md,
  # except the `$MOUNT_BAZEL_CACHE` part.