implementations, convert request handlers to use new python concurrent
framework, excise GfeScript and GfeScriptExecutor from the system.
Change-Id: I801b7b9812a72fdfc72975a311d8dc3806cda152
Former-commit-id: 7c74510723 [formerly edaef1edf93ed7d7f626591ecfd86fb4c76f92e8]
Former-commit-id: 566927980a