tests: fix qemu-login-expect fail-marker guard, docstring flags, retry count

Post-review fixes:
- Phase 2 no longer breaks early when only --fail_marker is set: the
  'if not args.pass_marker: break' guard skipped all output reads, so a
  fail marker was never detected (exit 0 instead of 1). Now breaks only
  when neither pass nor fail markers are configured.
- docstring referenced --pass/--fail; argparse registers
  --pass_marker/--fail_marker. Align the docstring.
- retry echo said 'attempt N/3' but the loop limit is 5 attempts; say /5.
- warn and skip malformed steps (missing expect:/send: prefix) instead of
  spinning in select until timeout.

local/scripts/qemu-login-expect.py

@@ -10,8 +10,8 @@ installed without sudo).
 
 Spec model: an ordered list of steps. Each step is `expect:<text>` (wait for
 the literal text in guest output) or `send:<text>` (write text + CR to the
-guest). After all steps, wait for `--pass <text>` to succeed, or `--fail
-<text>` / timeout to fail.
+guest). After all steps, wait for `--pass_marker <text>` to succeed, or
+`--fail_marker <text>` / timeout to fail.
 """
 import argparse
 import os
@@ -98,6 +98,10 @@ def main() -> int:
                 i += 1
                 deadline = time.monotonic() + args.timeout
                 continue
+        if not step.startswith("send:") and not step.startswith("expect:"):
+            print(f"WARN: ignoring malformed step (want expect:/send: prefix): {step!r}", file=sys.stderr)
+            i += 1
+            continue
         r, _, _ = select.select([out], [], [], 0.5)
         if r:
             chunk = os.read(out.fileno(), 65536)
@@ -119,7 +123,7 @@ def main() -> int:
         while not state["failed"]:
             if state["passes"] and len(state["passes"]) == len(args.pass_marker):
                 break
-            if not args.pass_marker:
+            if not args.pass_marker and not args.fail_marker:
                 break
             if time.monotonic() > deadline:
                 break

local/scripts/test-iommu-qemu.sh

@@ -136,7 +136,7 @@ if [[ "$check_mode" -eq 1 ]]; then
         fi
         if [[ ( $rc -eq 3 || $rc -eq 137 ) && $attempt -lt 5 ]]; then
             attempt=$((attempt + 1))
-            echo "QEMU exited before completing the check; retrying (attempt $attempt/3)"
+            echo "QEMU exited before completing the check; retrying (attempt $attempt/5)"
             sleep 2
             continue
         fi

local/scripts/test-ps2-qemu.sh

@@ -118,7 +118,7 @@ if [[ "$check_mode" -eq 1 ]]; then
         fi
         if [[ ( $rc -eq 3 || $rc -eq 137 ) && $attempt -lt 5 ]]; then
             attempt=$((attempt + 1))
-            echo "QEMU exited before completing the check; retrying (attempt $attempt/3)"
+            echo "QEMU exited before completing the check; retrying (attempt $attempt/5)"
             sleep 2
             continue
         fi

local/scripts/test-timer-qemu.sh

@@ -116,7 +116,7 @@ if [[ "$check_mode" -eq 1 ]]; then
         fi
         if [[ ( $rc -eq 3 || $rc -eq 137 ) && $attempt -lt 5 ]]; then
             attempt=$((attempt + 1))
-            echo "QEMU exited before completing the check; retrying (attempt $attempt/3)"
+            echo "QEMU exited before completing the check; retrying (attempt $attempt/5)"
             sleep 2
             continue
         fi

local/scripts/test-usb-storage-qemu.sh

@@ -143,7 +143,7 @@ while true; do
     fi
     if [[ ( $rc -eq 3 || $rc -eq 137 ) && $attempt -lt 5 ]]; then
         attempt=$((attempt + 1))
-        echo "QEMU exited before completing the check; retrying (attempt $attempt/3)"
+        echo "QEMU exited before completing the check; retrying (attempt $attempt/5)"
         sleep 2
         continue
     fi