Skip ConnOnActivityStartTest and CoreSettingsObserverTest.

- ConnOnActivityStartTest is consistently failing because the device
doesn't have network connectivity. This test probably needs to be moved to a
different test suite but for now just skipping the tests.
- CoreSettingsObserverTest is failing because the test depends on a mock
settings provider but since the Settings class caches the provider
object, the test will end up using real settings provider and fails.

Bug: 38432755
Bug: 38433611
Test: N/A
Change-Id: I0504d9f0df14a0f952e32c8572eefe9ccfebfd2c