Update logic for enterprise connections

Treat as a failure if the default data connection has the same CID or if
the default data connection doesn't exist.
Also update the logic for enterprise capability so only enterprise and
internet don't exist at the same time.

Bug: 182953365
Test: atest DcTrackerTest, DataConnectionTest
Change-Id: Ica20a458f46850d14a755a29a030d3eaa820b48f
Merged-In: Ica20a458f46850d14a755a29a030d3eaa820b48f