WebView: fix broken WebViewSslTest

An SSL-related bug fix in WebView (http://crrev/c/1259123) exposed an
error in this CTS test.

Although the test's original comment still rings true (failing the
client is a non-recoverable error), the behavior change in WebView
correctly triggers a recoverable error first (since we don't trust the
server certificate).

Bug: 123030084
Test: atest CtsWebkitTestCases:WebViewSslTest#testSecureServerRequiringClientCertDoesCancelRequest
Change-Id: I2c32e9d3c6269d6d139ce15f026ceb4b40bb241c