[tumble] Set default deadline to 4 min 30sec
[tumble] Set default deadline to 4 min 30sec

Change-Id: Idc735791f2f5dc44c173b0753633997ce0ad43c1
Reviewed-on: https://chromium-review.googlesource.com/1121105
Reviewed-by: Robbie Iannucci <40f3d43a28ebae3cb819288542e1c84d73d962d5@chromium.org>
Commit-Queue: Ryan Tseng <2190fe9a39b4920ec7bd59c848ec5cccd163056f@chromium.org>

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