CI: Disable stack cost retrieval to stop job hang

CI: Disable stack cost retrieval to stop job hang

This is a temporary workaround to address critical job hangs caused
by lftools openstack stack cost command lacking timeout handling.

Problem (IT-28614):
  The lftools stack cost command hangs indefinitely when:
  - Pricing API (pricing.vexxhost.net) is slow/unresponsive
  - OpenStack SDK queries for nested stacks take too long
  - Network operations lack timeout parameters

  This causes:
  - Jobs stuck at 'Retrieving stack cost for: <stack-name>'
  - Downstream jobs waiting on checkpoints indefinitely
  - Jenkins queue buildup (66+ jobs waiting reported)
  - Requires manual intervention to cancel stuck jobs

Solution:
  Disable stack cost retrieval by commenting out the lftools call
  and hardcode stack cost to 0 in the stack-cost file.

Known Regression:
  Stack costs will be reported as 0 in archived cost.csv files,
  losing cost tracking data for OpenStack resources. Instance-level
  costs are still collected via job-cost.sh pricing API calls.

Root Cause:
  lftools/openstack/stack.py cost() function lacks:
  - timeout parameter for urllib.request.urlopen() (line 87)
  - timeout handling for OpenStack SDK resource enumeration
  - graceful degradation on network failures

Next Steps:
  1. Implement timeout handling in lftools
  2. Once lftools is fixed, revert this workaround
  3. Create tracking issue for the regression (stack costs = 0)

This stopgap prioritizes job reliability over cost data collection.

Issue-ID: IT-28614
Change-Id: I9d054347e485f4843c7287aec49fb7aff0962e96
Signed-off-by: Anil Belur <abelur@linuxfoundation.org>