[Vendor] Update go-redis to v8.5.0 (#13749)

* Update go-redis to v8.4.0

* github.com/go-redis/redis/v8  v8.4.0 -> v8.5.0

* Apply suggestions from code review

Co-authored-by: zeripath <art27@cantab.net>

* TODO

* Use the Queue termination channel as the default context for pushes

Signed-off-by: Andrew Thornton <art27@cantab.net>

* missed one

Signed-off-by: Andrew Thornton <art27@cantab.net>

Co-authored-by: zeripath <art27@cantab.net>

vendor/github.com/go-redis/redis/v8/.travis.yml

@@ -0,0 +1,20 @@
+dist: xenial
+language: go
+
+services:
+  - redis-server
+
+go:
+  - 1.14.x
+  - 1.15.x
+  - tip
+
+matrix:
+  allow_failures:
+    - go: tip
+
+go_import_path: github.com/go-redis/redis
+
+before_install:
+  - curl -sSfL https://raw.githubusercontent.com/golangci/golangci-lint/master/install.sh | sh -s --
+    -b $(go env GOPATH)/bin v1.32.2