Pause the existing rollout if a hotfix commit lands

[kitallis]

Problem

When there's a phased release in progress, and we land another commit (essentially as a hotfix) and the release goes into hotfix mode

We should go ahead and pause the previous rollout running against the previous commit.

Steps to Reproduce

Land a commit when a phased release is in progress

Expected behavior

The last rollout should pause/halt automatically when a new hotfix commit lands.