Fix for mConnectTimeMillis being incorrectly set

mConnectTimeMillis should be 0 at construction so that
it is correctly updated in CallsManager.markCallAsActive.

To take care of the case where CDMA conference calls go directly
into active mode, explictly set the connection time when the
conference call is created.

Bug: 17464436
Change-Id: I2e1ec98aa18a3993e1356387edeb040672826f3f