qa/workunits/rbd: update to mirror group snapshot tests
Updated tests:
• test_odf_failover_failback - Update retry_promote screnario to limit retries to
10000 attempts
Disabled tests:
• test_create_group_with_images_then_mirror_with_regular_snapshots scenario 1
test sometimes fails as removed regular snapshot remains on secondary cluster
after new mirror group snapshot is sync complete
Helpers:
- get_pool_image_count() $XMLSTARLET variable shouldn't be used anymore