(re)define the definition of "provisioned"

Specifically:

    [1] provide a hasIPv4(), and
    [2] a hasIPv6()

each of which requires an IP address, a default route, and
address-family-specific DNS servers to evaluate to true.

Additionally:

    [3] redefine isProvisioned() to return the logical OR
        of [1] and [2] above.

Any external caller can still use any of the has*() methods to
construct its own, different definition of "provisioned".

Bug: 17769720
Change-Id: Ia692fb8508484ff403d3920c94d0e1db4563f807