branch_api: silently proceed when branch already exists

Previously we'd only proceed here if --force were enabled. However,
Cindy got hit with an error here even when it was her first attempt at
branching. I suspect the request to Gerrit might've been retried

Anyway, this doesn't actually change the program's behavior in a
meaningful way, since the program fails prior to this error, at the
following block, if manifest-internal has already been branched.

TEST=tests pass

Change-Id: Ib9b5802ad9a386dc46178a394b34e25f1fb288e8
Reviewed-by: Navil Perez <>
Commit-Queue: Sean Abraham <>
Tested-by: Sean Abraham <>
3 files changed