Patroni doesn't filter out some not allowed options from pg_basebackup (#3015)

When running `pg_basebackup` to bootstrap a replica, Patroni sanitizes
the custom user options that come from `postgresql.basebackup` configuration
section using the `process_user_options` method.

However, there is a bug in that method: it filters out not allowed options
that are in the format `- setting`, but not the ones in the format
`- setting: value` from `postgresql.basebackup`.

An example of that issue is the `dbname` setting. If you specify something
like this in the configuration file:

```yaml
postgresql:
  basebackup:
    - dbname: "host=RANDOM"
```

You end up with `--dbname` being specified twice for `pg_basebackup`, with
`--dbname='host=RANDOM'` taking precedence as it comes up later in the
command.

This commit fixes that issue by adding a `continue` statement when
the setting in format `- setting: value` is not allowed, thus skipping
it.

---------

Signed-off-by: Israel Barth Rubio <[email protected]>

tests/test_bootstrap.py

@@ -142,6 +142,16 @@ class TestBootstrap(BaseTestPostgresql):
                     (), error_handler
                 ),
                 ["--key=value with spaces"])
+            # not allowed options in list of dicts/strs are filtered out
+            self.assertEqual(
+                self.b.process_user_options(
+                    'pg_basebackup',
+                    [{'checkpoint': 'fast'}, {'dbname': 'dbname=postgres'}, 'gzip', {'label': 'standby'}, 'verbose'],
+                    ('dbname', 'verbose'),
+                    print
+                ),
+                ['--checkpoint=fast', '--gzip', '--label=standby'],
+            )
 
     @patch.object(CancellableSubprocess, 'call', Mock())
     @patch.object(Postgresql, 'is_running', Mock(return_value=True))