proxy: allow booleans in pool structure
proxy: allow booleans in pool structure

the return value passed from mcp_config_pools() is adjusted and copied
into the worker VM's so the types are limited. This adds the boolean
type to allowable list.

memcached/memcached,memcached/memcached,memcached/memcached,memcached/memcached,memcached/memcached