Fix netconf port validation and minor doc change (#24210)

* Fix netconf port validation and minor doc change

Add check to confirm if `validate_*` funcion is
callable.

Add `config_format` in `junos_facts` documentation

* Fix review comments

lib/ansible/modules/network/junos/junos_facts.py

@@ -46,6 +46,15 @@ options:
     required: false
     default: "!config"
     version_added: "2.3"
+  config_format:
+    description:
+      - The I(config_format) argument specifies the format of the configuration
+         when serializing output from the device. This argument is applicable
+         only when C(config) value is present in I(gather_subset).
+    required: false
+    default: text
+    choices: ['xml', 'set', 'text', 'json']
+    version_added: "2.3"
 """
 
 EXAMPLES = """

lib/ansible/modules/network/junos/junos_netconf.py

@@ -139,7 +139,7 @@ def map_params_to_obj(module):
     for key, value in iteritems(obj):
         # validate the param value (if validator func exists)
         validator = globals().get('validate_%s' % key)
-        if all((value, validator)):
+        if callable(validator):
             validator(value, module)
 
     return obj