Fix short_description flag in plugins, role modules and templates

Before "short description" was used in most plugins, modules and also
in the new module templates.

ansible-doc was therefore not showing the short description. To fix the
issue the flag was renamed to short_description instead.

Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=2121362
       'ansible-doc' -l lists most idm modules as 'UNDOCUMENTED'

utils/templates/ipamodule+member.py.in

@@ -32,7 +32,7 @@ ANSIBLE_METADATA = {
 DOCUMENTATION = """
 ---
 module: ipa$name
-short description: Manage FreeIPA $name
+short_description: Manage FreeIPA $name
 description: Manage FreeIPA $name and $name members
 extends_documentation_fragment:
   - ipamodule_base_docs

utils/templates/ipamodule.py.in

@@ -32,7 +32,7 @@ ANSIBLE_METADATA = {
 DOCUMENTATION = """
 ---
 module: ipa$name
-short description: Manage FreeIPA $name
+short_description: Manage FreeIPA $name
 description: Manage FreeIPA $name
 extends_documentation_fragment:
   - ipamodule_base_docs