Fix stderr false return value (#22845)

* ensure exit_json does not fail from stderr=False

- do a little bit of safety-checking in exit_json to not try to .splitlines() on a boolean
- remove the stderr=boolean from uri.py, this is the only spot that uses it (at least so obviously)
- add unit tests that call exit_json. These are useless because the stderr parsing is in _execute_module and is difficult to mock; deleting these tests after the commit.

* remove added unit tests per prev commit

exit_json doesn't do the param parsing, that is buried deep inside _execute_module.

lib/ansible/modules/network/basics/uri.py

@@ -425,15 +425,14 @@ def main():
         # and the filename already exists.  This allows idempotence
         # of uri executions.
         if os.path.exists(creates):
-            module.exit_json(stdout="skipped, since %s exists" % creates,
-                             changed=False, stderr=False, rc=0)
+            module.exit_json(stdout="skipped, since %s exists" % creates, changed=False, rc=0)
 
     if removes is not None:
         # do not run the command if the line contains removes=filename
         # and the filename do not exists.  This allows idempotence
         # of uri executions.
         if not os.path.exists(removes):
-            module.exit_json(stdout="skipped, since %s does not exist" % removes, changed=False, stderr=False, rc=0)
+            module.exit_json(stdout="skipped, since %s does not exist" % removes, changed=False, rc=0)
 
     # Make the request
     resp, content, dest = uri(module, url, dest, body, body_format, method,