Calls to net.Dial* are prohibited with GopherJS. This can happen if the
client's transport is set by the user.
This change forces transportForConfig to return nil when the client
package is compiled with gopherjs, in order to make sure that a call to
newClient returns a client with a nil transport.
Change-Id: I577457bd7d924d31710168086dc2b394df3d1ae0
mpl