Fix usage of `clone` to not clone prototypes in create*Client().

Commit f49e2c2 introduced potential cloning of given `options.log`
Bunyan Logger objects in the `create{Json,String,Http}Client()` APIs.
This would result in an abort on the first log write:

    Assertion failed: (args.Holder()->InternalFieldCount() > 0), function WriteStringImpl, file ../src/stream_wrap.cc, line 298.
    Abort trap

Note: This also involves a semantic change in that only a *shallow*
copy of `options` is done for createServer, createClient, and
create*Client methods.