test/stats.bats: improve test case
test/stats.bats: improve test case

1. Ensure that stats are shown for the particular ID.

2. Simplify json checks:
   - use "here file" instead of echo and pipe
   - remove intermediate variable
   - remove useless run and status checks (set -e is sufficient

Signed-off-by: Kir Kolyshkin <3a017b8ddb3f9cf3e4a59978b004111bdeb97f08@gmail.com>

kubernetes-incubator/cri-o,kubernetes-incubator/ocid,nalind/cri-o,kubernetes-incubator/cri-o,kubernetes-incubator/cri-o,nalind/cri-o,kubernetes-incubator/ocid,kubernetes-incubator/ocid,kubernetes-incubator/cri-o,nalind/cri-o