casclient: set timeout for batch RPCs
casclient: set timeout for batch RPCs

This is to follow http://b/204733388#comment16

Bug: b/204733388
Change-Id: I6c567576930b214e51084184c79c73ec886916fa
Reviewed-on: https://chromium-review.googlesource.com/c/infra/luci/luci-go/+/3275038
Commit-Queue: Takuto Ikuta <71927f930fca81015e0f496c65cd126ab1a692e3@chromium.org>
Commit-Queue: Junji Watanabe <aaef61ef98ffea505db831f310be2a0eb8492537@google.com>
Auto-Submit: Takuto Ikuta <71927f930fca81015e0f496c65cd126ab1a692e3@chromium.org>
Reviewed-by: Junji Watanabe <aaef61ef98ffea505db831f310be2a0eb8492537@google.com>

luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go