Change DcTracker construction so only initialization is preformed.

In initApnContexts applyNewState and onSetDependency met could cause
calls to trySetupData which can send notifications or even try to
bring up a connection. This can cause problems as not all objects are
initialized. In particular when I tried to change ApnContext#isReady
to be false it caused a call to mPhone.notifyDataConnection but mPhone
wasn't completely initialized and an NPE occurred.

Bug: 9022095
Change-Id: I6d1bf350f2803aa62fa21b6a6759685456bef6eb