Docs: add info how to cope with a protocol-related connection error using login_unix_socket argument (#420)

(cherry picked from commit f1d63e3fc8)

plugins/modules/mysql_role.py

@@ -126,6 +126,9 @@ extends_documentation_fragment:
 '''
 
 EXAMPLES = r'''
+# If you encounter the "Please explicitly state intended protocol" error,
+# use the login_unix_socket argument, for example, login_unix_socket: /run/mysqld/mysqld.sock
+
 # Example of a .my.cnf file content for setting a root password
 # [client]
 # user=root