Improve risky-shell-pipe rule matching (#1453)

Removes one false positive case where user set ignore_errors: true,
case in which the rule does not make much sense.

Fixes: #1250

Author: ssbarnea

src/ansiblelint/rules/ShellWithoutPipefail.py

@@ -2,6 +2,7 @@
 from typing import Any, Dict, Union
 
 from ansiblelint.rules import AnsibleLintRule
+from ansiblelint.utils import convert_to_boolean
 
 
 class ShellWithoutPipefail(AnsibleLintRule):
@@ -39,4 +40,5 @@ def matchtask(self, task: Dict[str, Any]) -> Union[bool, str]:
         return bool(
             self._pipe_re.search(unjinjad_cmd)
             and not self._pipefail_re.match(unjinjad_cmd)
+            and not convert_to_boolean(task['action'].get('ignore_errors', False))
         )

test/TestShellWithoutPipefail.py

@@ -65,6 +65,10 @@
     - shell: |
         set -o pipefail
         df | grep '/dev'
+
+    - name: should not fail due to ignore_errors being true
+      shell: false | cat
+      ignore_errors: true
 '''