Multi_vms_with_stress: ensure vms can start with stress workload running on host

[rh-jugraham]

Case ID: VIRT-301893

Automates the case that tests that multiple vms can use #host_only_cpu to start when stress workload is running on the host.

Test steps:
1. Prepare 3 vms that each have even vcpu number around 2/3 of # host_online_cpu
2. Start stress workload on the host
3. Start all vms and verify vms could be logged in normally
4. Verify all vms could be gracefully shutdown successfully

Evidence of tests passing:

(.libvirt-ci-venv-ci-runtest-TSPbXe) [root@ampere-mtsnow-altramax-31 ~]# avocado run --vt-type libvirt multi_vms_with_stress
No python imaging library installed. Screendump and Windows guest BSOD detection are disabled. In order to enable it, please install python-imaging or the equivalent for your distro.
No python imaging library installed. PPM image conversion to JPEG disabled. In order to enable it, please install python-imaging or the equivalent for your distro.
No python imaging library installed. Screendump and Windows guest BSOD detection are disabled. In order to enable it, please install python-imaging or the equivalent for your distro.
No python imaging library installed. PPM image conversion to JPEG disabled. In order to enable it, please install python-imaging or the equivalent for your distro.
JOB ID     : f8b4b60d59e7cf3d867104d46833fe6c8eb9e868
JOB LOG    : /var/log/avocado/job-results/job-2024-10-24T10.41-f8b4b60/job.log
 (1/7) type_specific.io-github-autotest-libvirt.multi_vms_with_stress: STARTED
 (1/7) type_specific.io-github-autotest-libvirt.multi_vms_with_stress: PASS (135.31 s)
 (2/7) type_specific.io-github-autotest-libvirt.multi_vms_with_stress: STARTED
 (2/7) type_specific.io-github-autotest-libvirt.multi_vms_with_stress: PASS (135.70 s)
 (3/7) type_specific.io-github-autotest-libvirt.multi_vms_with_stress: STARTED
 (3/7) type_specific.io-github-autotest-libvirt.multi_vms_with_stress: PASS (135.55 s)
 (4/7) type_specific.io-github-autotest-libvirt.multi_vms_with_stress: STARTED
 (4/7) type_specific.io-github-autotest-libvirt.multi_vms_with_stress: PASS (138.33 s)
 (5/7) type_specific.io-github-autotest-libvirt.multi_vms_with_stress: STARTED
 (5/7) type_specific.io-github-autotest-libvirt.multi_vms_with_stress: PASS (138.49 s)
 (6/7) type_specific.io-github-autotest-libvirt.multi_vms_with_stress: STARTED
 (6/7) type_specific.io-github-autotest-libvirt.multi_vms_with_stress: PASS (137.15 s)
 (7/7) type_specific.io-github-autotest-libvirt.multi_vms_with_stress: STARTED
 (7/7) type_specific.io-github-autotest-libvirt.multi_vms_with_stress: PASS (138.84 s)
RESULTS    : PASS 7 | ERROR 0 | FAIL 0 | SKIP 0 | WARN 0 | INTERRUPT 0 | CANCEL 0
JOB HTML   : /var/log/avocado/job-results/job-2024-10-24T10.41-f8b4b60/results.html
JOB TIME   : 976.49 s