Fix getName callback response unneeded deserialization

[IlyaSemenov]

The current proxied getName callback is broken. The data returned by user-provided callback is passed to IPC as is:

tdl-multiprocess/lib/Client.js

Line 68 in 01fde12

this.authMethods.getName = loginDetails.getName

tdl-multiprocess/lib/Client.js

Lines 39 to 41 in 01fde12

	this.ipc.register('getName', () => {
	return this.authMethods.getName()
	})

but then the child tries to parse it as JSON (and crashes):

tdl-multiprocess/lib/Child.js

Lines 73 to 78 in 01fde12

	details.getName = () => {
	return ipc.exec('getName')
	.then(result => {
	return JSON.parse(result)
	})
	}

The account registration is therefore broken with tdl-mutltiprocess.

The PR removes the unneeded deserialization (honestly, I'm not sure why do you want to serialize other request/responses..node-ipc-promise seems to be doing that already just fine.)