qa/suites/rbd: fix sporadic "rx-only direction" test failures

[idryomov]

The existing

xmlstarlet sel -t -v  '//mirror/peers/peer[1]/uuid')" = ""

test is bogus since a tx-only peer gets added after the remote rbd-mirror daemon pings the local cluster. It happened to pass most of the time because xmlstarlet filter just failed on an empty peers array, producing the wrongly expected empty string by accident.

Fixes: https://tracker.ceph.com/issues/58688
Signed-off-by: Ilya Dryomov idryomov@gmail.com

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[idryomov]

Evidence of an empty peers array (a sleep in the fixed test):

2023-02-10T16:07:29.234 INFO:tasks.workunit.cluster1.client.mirror.smithi129.stderr:+ testlog 'TEST: verify rx-only direction'
2023-02-10T16:07:29.234 INFO:tasks.workunit.cluster1.client.mirror.smithi129.stderr:+ tee -a /tmp/tmp.epCfqAEDJb/rbd-mirror.test.log
2023-02-10T16:07:29.234 INFO:tasks.workunit.cluster1.client.mirror.smithi129.stderr:++ date '+%F %T'
2023-02-10T16:07:29.235 INFO:tasks.workunit.cluster1.client.mirror.smithi129.stderr:+ echo 2023-02-10 16:07:29 TEST: verify rx-only direction
2023-02-10T16:07:29.235 INFO:tasks.workunit.cluster1.client.mirror.smithi129.stderr:2023-02-10 16:07:29 TEST: verify rx-only direction
2023-02-10T16:07:29.235 INFO:tasks.workunit.cluster1.client.mirror.smithi129.stderr:+ rbd --cluster cluster2 --pool mirror mirror pool info --format json
2023-02-10T16:07:29.235 INFO:tasks.workunit.cluster1.client.mirror.smithi129.stderr:+ jq -e '.peers[0].direction == "rx-only"'
2023-02-10T16:07:29.274 INFO:tasks.workunit.cluster1.client.mirror.smithi129.stdout:true
2023-02-10T16:07:29.275 INFO:tasks.workunit.cluster1.client.mirror.smithi129.stderr:+ rbd --cluster cluster1 --pool mirror mirror pool info --format json
2023-02-10T16:07:29.275 INFO:tasks.workunit.cluster1.client.mirror.smithi129.stderr:+ jq -e '.peers | length > 0'
2023-02-10T16:07:29.316 INFO:tasks.workunit.cluster1.client.mirror.smithi129.stdout:false
2023-02-10T16:07:29.317 INFO:tasks.workunit.cluster1.client.mirror.smithi129.stderr:+ sleep 1
2023-02-10T16:07:30.319 INFO:tasks.workunit.cluster1.client.mirror.smithi129.stderr:+ rbd --cluster cluster1 --pool mirror mirror pool info --format json
2023-02-10T16:07:30.319 INFO:tasks.workunit.cluster1.client.mirror.smithi129.stderr:+ jq -e '.peers | length > 0'
2023-02-10T16:07:30.357 INFO:tasks.workunit.cluster1.client.mirror.smithi129.stdout:true
2023-02-10T16:07:30.358 INFO:tasks.workunit.cluster1.client.mirror.smithi129.stderr:+ rbd --cluster cluster1 --pool mirror mirror pool info --format json
2023-02-10T16:07:30.358 INFO:tasks.workunit.cluster1.client.mirror.smithi129.stderr:+ jq -e '.peers[0].direction == "tx-only"'
2023-02-10T16:07:30.394 INFO:tasks.workunit.cluster1.client.mirror.smithi129.stdout:true

[idryomov]

https://pulpito.ceph.com/dis-2023-02-10_14:32:40-rbd-main-distro-default-smithi/
https://pulpito.ceph.com/dis-2023-02-10_15:37:05-rbd-main-distro-default-smithi/

(ran on main since this is a test-only change)