Remove tests related to LegacyVpnRunner.

LegacyVpnRunner is removed, remove the following related tests:
1. testStartRacoonNumericAddress
2. testStartRacoonHostname
3. testStartPptp
4. testStartPptp_NoMppe

Create a new test that asserts UnsupportedOperationException for
the VPN types in those tests.

Bug: 161776767
Test: atest FrameworksNetTests
Change-Id: Id66d09ea54576ca4c641e8f69d104dc26a42c46b
1 file changed