virsh_domjobinfo: fix pipe file read stuck when background virsh cmd failed

Since libvirt 11.5.0, the virsh dump --live option has been disabled and now returns an error message.
This causes the test to hang while attempting to read the virsh dump pipe file's input.

The fix implements subprocess.communicate() to handle the background command interaction:
Command failure: the test aborts immediately with the error message.
Command success: original logic remains unchanged.
Note: If the background command fails after the timeout period, this likely indicates a libvirt issue, so no changes are made for now.

Signed-off-by: Liang Cong <[email protected]>

Author: liang-cong-red-hat

libvirt/tests/src/virsh_cmd/domain/virsh_domjobinfo.py

@@ -150,6 +150,14 @@ def cmp_jobinfo(result, info_list, job_type, actions):
         else:
             process = get_subprocess(action, vm_name, tmp_pipe, None)
 
+        try:
+            _, stderr = process.communicate(timeout=6)
+            if process.returncode:
+                os.unlink(tmp_pipe)
+                test.error('Background cmd met unexpected failure of %s, abort the test.' % stderr)
+        except subprocess.TimeoutExpired:
+            logging.debug("Background cmd is still running.")
+
         f = open(tmp_pipe, 'rb')
         dummy = f.read(1024 * 1024).decode(locale.getpreferredencoding(), 'ignore')