ci: avoid using potentially missing xargs during emergency debugprinting

Author: anokfireball

features/_rescue/file.include/etc/systemd/system/emergency.service.d/debugprint.conf

@@ -2,9 +2,8 @@
 StandardOutput=journal+console
 StandardError=journal+console
 ExecStartPre=/bin/sh -c ' \
-  systemctl --failed --no-legend --no-pager | awk "{print \$2}" | \
-  xargs -r -I{} sh -c " \
-    echo \"\\n=== FAILED UNIT: {} ===\\n\"; \
-    journalctl -b -u {} --no-pager || true; \
-  "'
+  for unit in $(systemctl --failed --no-legend --no-pager | awk "{print \$2}"); do \
+    echo "\n=== FAILED UNIT: $unit ===\n"; \
+    journalctl -b -u "$unit" --no-pager || true; \
+  done'
 TimeoutStartSec=20s