Fix server method registered as object without options

[devinivy]

Currently (hapi v17.1.1, node v8, OSX) the following error occurs when attempting to register a server method of the form server.method({ name, method }) (without options),

      Cannot read property 'generateKey' of undefined

      at module.exports.internals.Methods._add (/hapi/lib/methods.js:51:40)
      at module.exports.internals.Methods.add (/hapi/lib/methods.js:37:18)
      at internals.Server.method (/hapi/lib/server.js:331:35)
      at it (/hapi/test/methods.js:98:16)

This PR offers a proposed fix and tests.

[lock]

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