nebraska: Fix failures_per_url implicit string conversion.

XML parsers can't implicitly convert int to str. We need to explicitly
do this.

Strangely enough this is not failing the unittest, but on a DUT.

BUG=None
TEST=nebraska_unittest

Change-Id: Ibe1f4a969e09d5f85d1a6f0f852681de295d972a
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/dev-util/+/2029928
Tested-by: Jae Hoon Kim <[email protected]>
Commit-Queue: Amin Hassani <[email protected]>
Auto-Submit: Amin Hassani <[email protected]>
Reviewed-by: Jae Hoon Kim <[email protected]>
2 files changed