Respect SkipPresubmit annotation for ConnectivityCoverageTests

Follow-up from aosp/2788197, the CL does not work since
SkipPresubmit annotation is not excluded from TEST_MAPPING for
ConnectivityCoverageTests.

Test: TH
Bug: 302325928
Change-Id: Ibfa509aadc9e54da14738714be46abd25f46f3fb