MB-12537: Remove double `__init__`

The `RestConnection` contains two definitions of `__init__`. The latter
one overrides the former. Hence the former can be replaced. Hence some
code to illustrate it:

    class Foo:
        def __init__(self):
            print("__init__ 1: {}".format(self))

        def __init__(self):
            print("__init__ 2: {}".format(self))

    if __name__ == '__main__':
        foo = Foo()
        print(foo)

The output will is:

    __init__ 2: <__main__.Foo object at 0x7f13d6d16ef0>
    <__main__.Foo object at 0x7f13d6d16ef0>

It's the same with Python2 and 3.

Change-Id: I22a94e89758278343c2b7917be0883e4678ec4c7
Reviewed-on: http://review.couchbase.org/42779
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Ketaki Gangal <ketakigangal@gmail.com>
Reviewed-by: Tommie McAfee <tommie@couchbase.com>