library: fix a bug in ceph_config module

`ceph config get` doesn't allow getting value when entity is 'global' so
it makes the module fail. Indeed, the module first tries to get the
current value of the option for idempotency concern.
The idea is to check in `ceph config dump` instead.

Closes: https://bugzilla.redhat.com/show_bug.cgi?id=2188319

Signed-off-by: Guillaume Abrioux <gabrioux@ibm.com>
(cherry picked from commit b28fe12)

library/ceph_config.py

@@ -13,6 +13,7 @@
     from module_utils.ceph_common import exit_module, build_base_cmd_shell, fatal  # type: ignore
 
 import datetime
+import json
 
 ANSIBLE_METADATA = {
     'metadata_version': '1.1',
@@ -84,22 +85,35 @@
 RETURN = '''#  '''
 
 
-def get_or_set_option(module: "AnsibleModule",
-                      action: str,
-                      who: str,
-                      option: str,
-                      value: str) -> Tuple[int, List[str], str, str]:
+def set_option(module: "AnsibleModule",
+               who: str,
+               option: str,
+               value: str) -> Tuple[int, List[str], str, str]:
     cmd = build_base_cmd_shell(module)
-    cmd.extend(['ceph', 'config', action, who, option])
-
-    if action == 'set':
-        cmd.append(value)
+    cmd.extend(['ceph', 'config', 'set', who, option, value])
 
     rc, out, err = module.run_command(cmd)
 
     return rc, cmd, out.strip(), err
 
 
+def get_config_dump(module: "AnsibleModule"):
+    cmd = build_base_cmd_shell(module)
+    cmd.extend(['ceph', 'config', 'dump', '--format', 'json'])
+    rc, out, err = module.run_command(cmd)
+    if rc:
+        fatal(message=f"Can't get current configuration via `ceph config dump`.Error:\n{err}", module=module)
+    out = out.strip()
+    return rc, cmd, out, err
+
+
+def get_current_value(who, option, config_dump):
+    for config in config_dump:
+        if config['section'] == who and config['name'] == option:
+            return config['value']
+    return None
+
+
 def main() -> None:
     module = AnsibleModule(
         argument_spec=dict(
@@ -135,16 +149,22 @@ def main() -> None:
     startd = datetime.datetime.now()
     changed = False
 
-    rc, cmd, out, err = get_or_set_option(module, 'get', who, option, value)
-    if rc:
-        fatal(message=f"Can't get current value. who={who} option={option}", module=module)
+    rc, cmd, out, err = get_config_dump(module)
+    config_dump = json.loads(out)
+    current_value = get_current_value(who, option, config_dump)
 
     if action == 'set':
-        if value.lower() == out:
+        if value.lower() == current_value:
             out = 'who={} option={} value={} already set. Skipping.'.format(who, option, value)
         else:
-            rc, cmd, out, err = get_or_set_option(module, action, who, option, value)
+            rc, cmd, out, err = set_option(module, who, option, value)
             changed = True
+    else:
+        if current_value is None:
+            out = ''
+            err = 'No value found for who={} option={}'.format(who, option)
+        else:
+            out = current_value
 
     exit_module(module=module, out=out, rc=rc,
                 cmd=cmd, err=err, startd=startd,