Fix typo with package bisector switch_to_good script

Fix error where cros_pkg_switch_to_good.sh was using the bad build files
if passed a file argument.

Test=Switch to good verification passed with cros_pkg bisector

Change-Id: Ie2d5e1e741ceb97ba05d6f827161d12c103d9e48
Reviewed-on: https://chrome-internal-review.googlesource.com/262466
Commit-Ready: Cassidy Burden <cburden@google.com>
Tested-by: Cassidy Burden <cburden@google.com>
Reviewed-by: Caroline Tice <cmtice@google.com>
1 file changed