Use HttpsURLConnection to by pass proxies.

In isMobileOk attempting to connect to clients3.google.com/generate_204 we
sometimes see a proxy server will not let the connection go to our
server and instead returns 200 instead of 204. By using Https we by pass
proxy servers and we will always connected to our server.

The number of loops is increased from 3 to 4 and half the the retires
will use Http and half will use Https.

I also, added mTestingFailures which can be set to true by setting
persist.checkmp.testfailures to 1. This will cause checkMobileProvisiong
to always fail so we can test https & http.

Bug: 9972012
Change-Id: I870606037dcffe5250843980517ac52218266e02