Avoid using SSLv3 in tests

With conscrypt and libcore dropping SSLv3 calling
setEnabledProtocols() with SSLv3 will fail.

Bug: 30977793
Test: cts-tradefed run singleCommand cts -m CtsLibcoreOkHttpTestCases && libcore/run-libcore-tests libcore/luni/src/test/java/libcore/java/net/URLConnectionTest.java
Change-Id: I0b7176a4a0246c5355b174546295cf7a02f1f9ee