Cronet QUIC test: skip if request fails

This specific test checks whether QUIC is used when it's enabled. If the
request fails the test should just be skipped to reduce flakiness (we've
another test in place for that specific case)

Bug: 267618889
Test: m && atest CtsNetHttpTestCasess
Change-Id: Ib18778c14cb4d27f079cb42948e5c3e6f35e2e92