Skip handling validation status for non default data connections

The non default data connections doesn't go through network validation
procedure but connectivity service report validation success always.
DcTracker incorrectly noted this as a good signal and later triggered
a recovery when bad network is reported for default data connection.
This causes unnecessary data stall recovery and causes lab test failure.

This CL adds a check to handle network validation events only from
data connections that goes through network validation.

Bug: 135292998
Test: atest com.android.internal.telephony.dataconnection.DcTrackerTest
Change-Id: Iebe429f24fb16fd2748ac63adf6f875c4b398d7d