Consolidate boolean/mk_boolean conversion functions into a single location

Consolidate the module_utils, constants, and config functions that
convert values into booleans into a single function in module_utils.

Port code to use the module_utils.validate.convert_bool.boolean function
isntead of mk_boolean.

lib/ansible/module_utils/rax.py

@@ -32,7 +32,6 @@ import os
 import re
 from uuid import UUID
 
-from ansible.module_utils.basic import BOOLEANS
 from ansible.module_utils.six import text_type, binary_type
 
 FINAL_STATUSES = ('ACTIVE', 'ERROR')