Prior to this commit, it was possible to pass a truthy non-string
value as the HTTP method to the HTTP client, resulting in an
exception being thrown. This commit adds validation to the method.
PR-URL: https://github.com/nodejs/node/pull/10111
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
