[roll] Roll infra/recipes [checkout] Fix checkout failure for multiple cherry-pick builds on same CL

Before this change, there's a bug when running multiple builds with
"cherry_pick_patches" on the same CL.

When using "cherry_pick_patches", the recipe leaves behind a branch
that's named after the CL number and patchset number.

Since the bot's checkout cache is reused for incremental builds, if a
subsequent build runs on the same CL and patchset on the same Swarming
bot, it attempts to create a branch of the same name using "git
checkout -b", but fails because the branch already exists.

Fix that by using a unique branch name.

Original-Original-Bug: 520150286
Original-Original-Reviewed-on: https://fuchsia-review.googlesource.com/c/infra/recipes/+/1640106
Original-Original-Revision: 7187af633d93b3ae4d3f6ea279d8bdd1182fb84f
GitOrigin-RevId: b2fe2b220029b9a2e523a4c368bac53cea36e9f8
Change-Id: Id0e4e140cf07bc629d2afea5978c2599038b6ea0
Reviewed-on: https://fuchsia-review.googlesource.com/c/integration/+/1640994
Cr-Commit-Position: refs/heads/main@{#194226}